Both will equal the performance of what most people could write themselves (i.e. if you re not an experienced game engine developer).

Whether it s worth learning (and buying since both Unity and Torque cost for iPhone development) you ll have to ask yourself two questions:

1. Is my game idea suited the engine?
2. Is my passion for programming or game design?

Looking at the range of games made with Unity, it seems very flexible because although it is a 3d engine, lots of 2d games have been made with it. The downside of using Unity for something very simple (say, a match-3 tile game) is that it s a bit over the top in terms of download size.

On the passion issue, some people like programming a lot and will always feel it s better to write the engine themselves. And that s OK. But if you have a great idea for a game and just want to bring it to market as soon as possible, and it requires 3d rendering, character animation, that sort of thing, using Torque or Unity is going to get you there a lot faster.

If you want to do 2d development you should have a look at cocos2d iphone it is implemented in cocoa free open source and very easy to pick up

I think time to market is important to consider - if your going to burn out after a short time and of the engines mentioned above will allow you to build and launch a game quickly compared to writing the engine & game from scratch.

Like U62 said, where is your passion?

Currently I m building a framework/engine and a game. Its a great learning experience, but we had to understand that it would take a long time (we have day jobs) and that we have to just keep chipping away at it. So far, the experience has been an eye opener and I ve learned a great deal ... however, would I do it again? Probably not - I think I prefer designing the game and coding game specific logic - not engine specific.

I ve done a lot of research on the platforms and I personally really like Unity. You can email them and request the iphone trial license.

Anyways, good luck!