a rented T6s is arriving here tomorrow...

I have a T6s and here are a few issues you might want to consider:

1.  Since you are interested in BIF, you might need to turn the camera on quickly to grab a shot.  If you quickly push on the lever to turn the camera on, do you end of in video instead?  The switch on my camera is stiff and that frequently happens to me.

2.  Do you need or want the touch screen?  If so, do you also carry the camera by the neck strap?  You will likely find that with the touch screen and carrying the camera against your chest, the camera will not automatically turn off and the battery will quickly run down.

3.  If you do night photography, decide how you will track the exposure time.  With my previous T3i, the counter was illuminated.  With the t6s, the counter cannot be seen in the dark.

4.  Decide if you want to totally rely on the auto exposure settings or do you frequently evaluate the scene and use eV to adjust the exposure?  If so, you will have a big problem.  With my T3i, I could look thru the viewfinder and easily adjust eV.  With the T6s, the adjustment is a nightmare.  (Unlock the Dial. Push the shutter button halfway. That permits a few seconds to make the adjustment.  Push very gently down on the wheel to gain traction and then turn the wheel to adjust.  Relock the wheel so it does not accidently change.)  See if you have the same problem I do in using the wheel.  Trying to turn the wheel requires downward pressure which instead activates the rocker switches build into the wheel.

As you might gather from the above issues, I think the camera was designed by a committee of Dilberts who had no idea about the needs of a photographer.