No it is not. I see a lot of people consider the GTX 750 and GTX 750 Ti for gaming and it isn't a good selection. First to answer your first question yes there is a good bit of difference unless I am mistaken and the GTX 750 Ti is much faster.
However here is the problem, Nvidia makes the GTX 750 cards with a new architecture they are working on which offers really low power consumption. The performance for every watt of power used went up greatly, but the performance itself stayed about the same. So the performance is on key with any Nvidia GTX 650 Ti, while costing considerably more. They are charging a large premium for that power saving, and because it can be used in computers with weak power supplies.
A much faster and better graphics card for gaming, staying around that price range, would be either:
AMD: R7 265, R9 270, R9 270x
Nvidia: GTX 660, GTX 760
If you want this for gaming one of these cards listed will give better performance and run high settings on modern games easily while costing around the same amount. The 750 Ti, in comparison, would get only medium settings with a few high settings enabled.