[Freeze]

There are some other things you need to think of.

Magazines: The G36 uses proprietary magazines, meaning that you can't share mags with people who are running M4s or M16s. The F2000 uses STANAGs plain and simple. Of course, you could always find a STANAG Mag conversion for the G36, but it doesn't perform very good and it's hard to find a combinations of mags and adapters that work.

Aftermarket Support: There are many accessories and mods for a G36 model (unless of course, the ARES is proprietary, then that eliminates this), whereas (as far as I know), there aren't many things you can change or modify on the F2000.

Also, the K in G36K doesn't mean "longer", it actually stands for "Kurz", which means "Short". I think that you are comparing it to the G36C (C for Compact), which lacks the sighted handle and has a shorter stock and front end.