Just to clarify, recent Canon "Rebel" series models:

Rebel T6i (750D) and T6s (760D) are nearly identical models. The T6s is a slight upgrade with an added LCD display and a few more direct controls.

T7i (800D) and 77D were respectively the successors to the two models above. (Yes, 77D is a "Rebel" even though Canon changed their naming convention.)

The T6 (1300D) and T7 (1500D, 2000D) are far more entry-level models. in fact, there's not a lot of difference between them. For example, both use a pertty ancient Digic 4 processor. The oldest of the other models on this list (T6i) use a Digic 6, while the newest (SL3/250D) uses a Digic 8. Neither T6 nor T7 even have a self-cleaning sensor, which is a standard feature on every other model listed here... even the SL1/100D!

The SL1 (100D) was the smallest and lightest weight DSLR anyone ever made, but has specs quite similar to T6... very entry-level.

SL2 (200D) and SL3 (250D) both got significant upgrades and, other than the autofocus system (which is a simple 9-point, like the T6 and T7), have specs closer to the T7i. There isn't a lot of difference between SL2 and SL3. Mostly, the latter got some video-related upgrades.

The T6, T7, SL1 use slower contrast detection autofocus in Live View. The T6i and T6s use what Canon calls a hybrid AF system in Live View, which is better than contrast detection. But it's not as fast and good as the Dual Pixel CMOS AF that all the other models on this list use.

T6, T7, SL1, SL2 and SL3 all use a simple 9-point AF system, much like what Canon introduced in 2004 in the EOS 20D. This system has a single, higher performance dual axis AF point at the center. The other 9 points are lower performance single axis.

T6i and T6s both use a 19-point AF system, all of which are the higher performance dual axis type. This is a somewhat simplified form of the AF system Canon introduced in the original EOS 7D in 2009.

The T7i and 77D have a 45-point AF system, all of which are higher performance dual axis, largely inherited from the 80D where Canon introduced it in 2016.

All the models listed have approx. 24MP sensors, except for the T6 and SL1, both of which use 18MP (similar to what was first intro'd in original 7D, 2009).

Look for D760 also, the European model number for the T6s. They are long out of warranty so you pay for service anyway and D760s came in as gray market and Canon will work on gray market for the regular service pricing.

I bought one for my wife early last year, a great bargain with 4 lenses and other accessories and she ignored it. Now yesterday she announced that since the Senior Center Photo Club hasn't been meeting for over a year I am devoting the 1-2 PM on Thursdays to teaching her more about photography. I gave her some lessons about 2 years ago and she now wants to learn to do more with both her SX50 and the D760, flash etc. Why the sudden interest, our special need son loves trains and she found a new model train club with a guy who teachs special needs people like him how to care for his trains and she wants good pictures of them together. (Jon is 29 with the mentality of a bright 5 year old.)

Before my lessons she was a lifelong "snap shot" picture taker. After a few composition lessons and a few trips to the park with some nice results: "Why didn't someone teach me this stuff 40 years ago?" I think my name is now "someone", but someone else" doesn't remember I tried and she just kept saying "You take the pictures." and then wanted me to also carry the movie(later video) camera and use both. Try walking through Disneyland with a 35mm and lenses and a movie camera. What, use one with each hand?