Is there a big difference in a full frame camera from a non-full frame camera

[jfo]

Kinda.  Multiplied by the fact that Canon's full-frame and crop-sensor models have different features and capabilities in addition to the sensor size.  What are you shooting?

Have you read through various articles online about this topic?

http://digital-photography-school.com/full-frame-sensor-vs-crop-sensor-which-is-right-for-you

http://www.petapixel.com/2010/10/02/full-frame-vs-crop-sensor-comparison/

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

http://www.photographybyvarina.com/photography/q-and-a/camera-format

[ScottyP]

I shot a crop (T3i most recently) for a while.  They will give you shots that are great.  If you were to print a picture from a crop and a FF, even a large one, you could not tell the difference between bodies.  (Lenses are another story!)

One difference with FF is all the shots you could not have gotten at all with the crop due to light.  FF gives you the ability to shoot acceptable-quality shots at much higher sensor-sensitivities (ISO settings) than a crop.  With a Rebel or other crop-sensor camera you begin to see "noise" in your images at ISO 400, and it is pretty rough by ISO 800.  You can shoot without flash or with a deeper depth of field in a lot of cases whereit wouldn't have worked on the crop. 

With a new FF like 5D3 or 6D (or 1DX!), you can shoot easily at 3200 or 5000 or 6400 with acceptable "noise" levels.

The FF also gives you a naturally wider angle in your shots, which the crop cameras narrow down.  The "18"mm "wide" end of the kit lens on a crop body is actually 28.8 mm when translated back into FF.  To get truly wide on a crop camera, you have to get an ultrawide lens, or even a "fisheye". 

That never bothererd me much, though, because the flip side of it is you get a 1.6x "boost" to your telephoto lenses, which I enjoyed more.

Also on a FF camera, you have a much better ability to shoot with a narrow depth of field, isolating your subject from a blurred background.  On a FF camera, f/4 is "wider" than f/2.8 was on a crop.

On the other hand, the FF bodies are tremendously more expensive than the crop bodies, particularly when comparing entry-level to entry-level.  For that kind of money, one can find ways to compensate or work around most of the limitations on the crop bodies!  A lot of it is a matter of personal taste, personal budget.