i did the same.
camera felt like a bit of a downgrade, but that's just my opinion. not that 3t's camera is bad, it's quite capable too but i feel the lowlight shots are better handled by the 6p.
3t is much more manageable in the hand of course.
development scene is similar so no issues here.
i felt like 3t gave me much better battery life, in large part due to the screen i suppose. and the screen is quite good, you won't notice any difference even though it's fhd. real world performance is quite similar but it does not heat up like the 6p (my 6p used to heat up occassionally)