I’ve read earlier posts about the iphone roughly being able to handle 7000 vertices on the screen at one time. These posts were all back when the original iphone and the 3g were around. How many vertices can the iPhone 4 handle? What kind of limitations are imposed over textures?
I find that you are more limited by the fill amount than actual vertices. If they only take a small part of the screen then you can have more. If they are front and center, taking up a lot of the screen, the iPad will have serious trouble with it.
It all just greatly depends on what else you are doing in your game too and how many FPS you need.
The easiest way to figure what your game can handle is to load a model and see what happens. I know it’s not a formula, but given the vast # of variables there is not a “easy” answer.
My latest game has 8200 verts on screen and 10200 triangles. It runs just fine. It was slower before but that was not due to vertices. It was due to # of draw calls.
So far the slowest device I have is my 1st gen iPhone, followed up by my iPad, then my iPod Touch 2nd Gen, and finally my iPhone 4. I test on my iPad and if it works there, I’m pretty sure it will run fine on everything but my 1st gen phone which is not supported any longer anyway.