Hard to say w/o knowing the system it will go into. And your display resolution.
But... it depends. Do you want the fastest fps or highest in-game quality settings?
The GTX 1060 3GB will out perform the GTX 1050 Ti by quite a bit. If you play at very high settings in class A games, you might see occasional stutter as memory is switched in and out... where as the extra gig of VRAM on the 1050 Ti you may not. Or at least not as often.
I had a 3GB 1060 for awhile. Never had an issue with the games I played at 1080p.