Bullet 2.73 should have better performance in most cases.
This produces an extra function call in the inner-loop.
This is likely negligible, and a proper optimizing compiler will remove the function call.
Somewhat unrelated, but I noticed SIMD_FORCE_INLINE pragmas in cpp files (simply do a global search and you will find them). As far as I know, not all compilers, if any at all, will inline code from cpp files, so this is a bit confusing
Yes, several compilers will optimize and inline the method if it is used in the same .cpp file. Even more interesting, a virtual method can be declared as 'inline' and if the type of the class is known at compile-time, it will be inlined.
Hope this helps,