The 1050 Ti and the RX 480 are two different levels of videocard, with the 480 being vastly superior. If you could get them at the same price then the 480 is the better deal by far.
That said, the power supply question is critical and not to be underestimated. The 1050 Ti comes in models that do not require a power connector. This means just about anyone can use one. The 480 requires a power connector. This means it's possible you might have to buy a new power supply depending on what you have now, which spoils the whole point of it being a good deal.
One last consideration, depending on the games you play, you may not need the extra performance of the 480. There are games, like Witcher 3 and Rise of the Tomb Raider, that benefit from...