That said, I suggest to always use Math, and switch to something like FMath if (after profiling) it's clear that Math causes a major bottleneck and that FMath's inaccuracies are within bounds of acceptability.
Yea, of corse
In my current case I'll only have one class wich uses some basic math relativly often. Therefore I can just try it out without too much hassle.
One thing wich is rather odd: with C/C++ lookup tables are slower
then doing it the proper way, because lookup tables needs to execute more commands. Well, it's more inaccurate than the über accurate java way in double precision. I wish there would be a float math lib and a hotspot compiler wich knows about it, too.
That would be pretty awesome