Hi Whitney and welcome to the forum: 😊
From what you have said, you have a divergent set of needs:
- I have a Sony a7riii for real estate, but I would rather use my t7.
- I primarily take wildlife and portraits.
So to consider the features you might need for these activities...
* Real estate photography: is best done with a full-frame camera, the uncropped Field of View (FoV) can make the most of the wide-angle lenses you need to capture a room.
* Wildlife photography, on the other hand, will benefit from the advantages in a cropped FoV and image density which is enhanced with a crop-sensor camera like your T7.
If you do combine both into one body, then I am working on the assumption you can write off the cost of your camera body against your business, thus offering you a discount to invest in more expensive gear. If that would not work, then we definitely need to know some kind of budget!
In the case where you prefer an all-in-one solution, I would tend towards a full-frame, fairly high pixel camera, with a pixel density that is able to give you both of those capabilities. You will be able to use the high pixel count of the FF sensor to crop the FoV and achieve similar results to those of a lower pixel count, crop-sensor body.
Without doubt the best gear right now is in Canon's R-series of Mirrorless Interchangeable Lens Cameras (MILCs), offering the best future investment value. For the following reasons:
a) The R3, R5 and R6 (and soon R7) all have In-Body-Image-Stabilization, which is brilliant for working hand-held, especially with long lenses. When you evolve to the RF lenses over time, many of their own optical IS will work with the IBIS to give huge levels of stabilization.
b) The R3, R5 and R6 (not sure about the R7 - it's crop sensor and not really on the market), have excellent dynamic range, enhancing capturing a range of light from dark to bright - great for your real-estate work in particular. Furthermore they can all work in much dimmer light with hugely-improved ISO performance.
c) The same three have Animal Eye Tracking: which you will likely find a game-changer for your wildlife work and portraiture. The ability to automatically find the eye and follow it is amazing.
If you choose from current Canon gear, I would suggest going for the 45MP Canon EOS R5 for the following reasons: the R3 is very expensive but only 24MP, while the R6 is only 20MP.
1. The full-frame sensor will work best with ultra-wide angle lenses for your work in real estate. If you eventually combine that with the yet-to-be-released RF 11-24 f/4 lens, you will have an awesome unit for your work. In the meantime continue to use the Sony.
2. For portrait work, you will gain the benefit of FF sensor's ability to generate a very shallow depth of field, and make the most of fast lenses - and there are quite a few in the new RF line-up that might work for you. That said, your existing Canon EF lenses will work with the new RF mount via an adapter. Canon do make a custom macro lens, but also a couple of brilliant portrait primes if that is what you prefer.
3. Wildlife: At the long end, the 45MP sensor can take quite a bit of cropping - if you were to crop right down to the same area as that of a Canon T7, then you would still get about 18MP resolution, but you can have the added benefit of the wide end of the zoom range. With the EF-RF adapter you can continue to use your Sigma 150-600 quite successfully - see the following sample images taken with the R5 and the Sigma 150-600 Contemporary.
I shall post a couple of very wide-angle shots taken with the Canon R5 and the EF 17-40mm, when there is enough light - it's winter in NZ and the sun is not up yet!
