First time poster. Better late than never, I suppose.
First, a little background.
For years, I was using a Nikon D60. Plenty fine entry-level DSLR. Then, in April of last year, I purchased a Canon 60D 18-135 kit. I also added the 70-300 USM, a Speedlite 320EX, and a Canon battery grip. I loved it. Shot some great pictures on it. However, a couple months later I had to sell it to fund another situation that came up. Missing out on having a camera, I picked up the Canon EOS M when it went on it's mega sale. For that, I have the Speedlite 90EX, and both US market EFM lense (18-55 and 22). I am formally trained in video production, but my love is photography. I do mostly hobbyist work, but am trying to venture into doing more photoshoots and paid work.
So, my predicament.
I love my little EOS M. I really do. Eventhough the focus issues have been more than well documented, it's a great little camera that takes every bit as good of an image as my 60D did..except for action. Studio work, car photoshoots, nature, etc. It does them all great. But you throw something moving into the mix and it's a disaster. I do not plan on getting rid of it. I plan on purchasing the EF/EFS lens adapter for it next week actually. However, I do realize the limitations of the camera. For the price, it's an unbeatable backup and a great camera to take with you when you don't want to lug around your whole setup to get a decent picture.
Now, where you come in.
I am looking to upgrade my setup. I am looking to purchase a new "go to" and the M will be my backup. And with the EF/EFS adapter, it'll be a good one at that. So, the main issue is that thus far, my paid work is few and far inbetween. Definitely nothing to purchase a camera body with, and barely even a Speedlite. But I'm hoping to change that. Up to this point, I'm completely self-funded. And thus, I'm trying to make the most economical, but well educated purchase I can. I will be using this as a complete all around workhorse. All sorts of photo, as well as video too. My list consists of the Rebel T5i body only, 70D, another 60D, *possibly* the 7D, and the 6D. I'd love a 5DIII, but there's no way I'm able to fund one at the moment.
Here's my breakdown. Feel free to chime in to your discression.
A proven, reliable go-to. Entry level, but has many solid features. Compact, while normally a good thing, fits a little awkwardly in my giant hands. My big issue with the T5i is that, although very cheap ($600 body only), it is more or less my EOS M with a viewfinder and more buttons/dials. It may not be enough of a change to warrant upgrading.
After having the 60D, I definitely love the siziing of the bigger cameras. The 70D essentially seems to be a 60D on steroids. At $1,100 for body and $1,300 with the 18-135 STM, I'd probably just opt for the kit. Seems like a great camera that particularly excels in video. Seems to be the current king of the crops, until the 7DII comes out.
Great camera. Does everything pretty well. The biggest bonus here, it's now SUPER cheap. At $700 body only, or $900 with the 18-135, it's a steal. Not to mention $300 cheaper than when I bought it. However, the technology has been surpassed by the 70D, and it may be worth the diference over it's older brother by now.
Although older, I know a ton of people that LOVE their 7D. It seems like the 70D has taken it's crop senosor king spot for now, but still a great camera. Big issue is it using CF Flash cards. Things are EXPENSIVE. I'd wait to see what's up with the 7DII, but I need to get a camera sooner than it'll be released. $1,400 for body, or $1,500 with the 18-135 / $1,600 with the 28-135 USM. At that price, it seems like the 70D is now also more competitively priced. Not to mention the SD card savings. But is it still "better"?
It would seem that this is the obvious choice. However, being self funded, $2,200 with the L lens kit is still costly. I would love to dive into the land of full-frame, but I'm still trying to be budget friendly. And with the 24-105, that'll cover most of what I'd need with addition of a couple primes and a 70-200 f/4 L to start.
As you can see, all varieties. Consumer, Prosumer, and Semi-Pro. In terms of my ability, I'm probably wedged between prosumer and semi-pro. I could definitely benefit from the 6D. Especially for what I shoot. But that's still a good chunk of change.
For the crop cameras, I was already planning on getting the EFS 17-55 2.8 USM, and the EFS 10-22 USM. Then either the EF 70-300 USM or 70-200 4 L for my zoom, as well as the EFS 60 macro and assorted primes.
For the 6D, the kit 24-105 as well as the EF 17-40 2.8 L, EF 24-70 2.8 L, and EF 70-200 2.8 L down the line. As well as a macro and some assorted primes of course.
Flash and other associated photo video equipment I'm good on. I am just at a loss of which way to go. Full frame sounds amazing. But then you have the associated cost with the upfront cost and future lenses. But if I stay crop, I can get what I need with the EFS lenses, an EF zoom, and be done with it. Definitely cheaper, but I don't know if it's the smartest choice.
So, I believe I'm done here. Sorry it was long-winded, but this has been plagueing me for the last few weeks. I hope someone else can help point me in a particular position. Please offer suggestions, and I'll be happy to answer any questions you may be able to interject.
First off, stop spending any more money on that EOS M ! I realize all the accolades you put on it but stop.
It went on super sale for a reason.
Simply put what I gathered from all you said, the Rebel T5i fits you. You will love it and it's price point.
Since the T5i and 60D are basically the same price, the major difference is the T5i has a touch screen LCD but the 60D has a control layout a bit more like the pro bodies (top LCD screen and a 2nd dial in the back.) If you either (a) shoot on manual a lot or (b) shoot in a semi-auto mode but frequently find yourself using exposure compensation, then having that 2nd dial in the back is a nice feature (there's a reason it's on all the pro bodies.) I *think* the 60D's physical dimensions are a tiny bit larger than a T5i but you'd have to read the specs (you mentioned the T5i seemed small in your hands.)
I do notice your overall theme of being able to afford the camera. For that reason, I'd cross the 7D off your list entirely. The 7D is optimized for action and can shoot 8 frames per second with it's 19 AF points ... all of which are "cross type" points. BUT... the 70D also has the 19 AF points (all of which are cross type) and shoots 7 frames per second... just 1 fps slower. On the 7D you can put an AF point into "spot" mode or "expanded" mode (which the 70D doesn't support). Basically the 70D comes close to replacing the 7D already. For video, nothing really beats the 70D because of it's dual pixel AF system on the sensor. If you do plan to shoot video... that feature is huge.
The 6D is basically a step-up from the 5D II. It uses an 11 point AF system, but like the 5D II (which used a 9 point AF system) _only_ the center point is cross-type. It's not designed for action photography, but it's fantastic for low light work. Keep in mind that there is no pop-up flash on a full-frame body so you'd have to get a trigger/controller/2nd speedlight, etc. to do off-camera flash.
...as a still camera the 70D is a nice upgrade from 60D primarily for it's autofocus system.
,,,but as a still camera, the four year old 7D is in many ways still more of an upgrade than 70D. 7D has even more advanced AF system, superior build/sealing, higher rated shutter/durability, slightly faster frame rate, 100% viewfinder, and more
...as a video camera, the 70D is the latest and greatest among all Canon cameras. T5i/700D is the next closest, but lacks the 70D's dual pixel focus system.
Otherwise, your logic is fine.
You should note that "going full frame", such as 6D, is more than just the cost of the camera body. You also will be looking at lenses. Your EF-S lenses won't be usable on the FF camera at all. Your 70-300mm would no longer enjoy anywhere near as much "reach" as it does on the crop sensor 60D. In general, lenses for FF are larger, heavier and more expensive than lenses for crop cameras can be.
You actually haven't mentioned what you shoot in any detail.... so it's a bit hard to really say which camera body might be best for your purpose(s). The 7D's forté is sports. The 6D is particular good for low light and/or really big prints. The 70D's standout capability is video. Of course, these are all usable for many purposes.... just talkin' about their particular strengths here, as compared to other models.