The obvious choice, if Ogre3D is too low level for you, would be NeoAxis: http://www.neoaxisgroup.com/
It's powered by Ogre, but is a complete game development platform.
It's targeting .NET so you can use C#, managed C++, VB.
So go for that. :)
Ogre3D is able to run on a range of mobile devices, like iPhone and Android. So it's not too big.
Don't mistake size for performance.
I am not sure if IrrLicht has an official iPhone support, but Ogre3D does.