GTX 1050ti 4gb or gtx 1060

Solution
In the games tested below, the 1060 3gb got 30% more fps than the 1050ti.

http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1060-3GB-vs-Nvidia-GTX-1050-Ti/3646vs3649

I suggest buying the best GPU within your budget. The 1060 3gb is better than the 1050ti. With that being said, both GPUs are budget GPUs and will struggle when it comes to longevity. They are great for budget rigs, but if you want a mid-range rig capable of playing 60fps at high settings then you should consider the 1060 6gb or the 580 8gb as the prices of these GPUs are finally reasonable.
In the games tested below, the 1060 3gb got 30% more fps than the 1050ti.

http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1060-3GB-vs-Nvidia-GTX-1050-Ti/3646vs3649

I suggest buying the best GPU within your budget. The 1060 3gb is better than the 1050ti. With that being said, both GPUs are budget GPUs and will struggle when it comes to longevity. They are great for budget rigs, but if you want a mid-range rig capable of playing 60fps at high settings then you should consider the 1060 6gb or the 580 8gb as the prices of these GPUs are finally reasonable.
 
Solution
What better explanation do you want?!?!?

Did you Watch the video???

It perform better!!!
Higher memory bandwidth!!!
Higer clock speed!!!
More CUDA cores!!!

Everything is better!!!

You want a complete PhD thesis? :-(
 
You can pair anything with anything else within reason, it all depends on how much you are willing to compromise. If you don't mind dropping details, even the 1050Ti can go a long way. I don't care all that much about graphics details since I can't even be bothered to notice them while moving and I ended up stretching my 1GB HD5770 until AMD dropped support two years ago. (I might have used it a while longer were it not for my multi-monitor desktop glitching a lot due to the GPU being perpetually low on VRAM when I started playing WoW again.)