Only real advice I have in this space:
1) ensure you get FIA belts. They don't cost any more but validity period is substantially longer
2) look for belts where the lock cannot be flipped upside down (or better said all the belts cannot be connected if the lock is upside down) and thus the lever ends up against your stomach instead of facing outwards. There have been cases of people doing this while in a rush and then subsequently having trouble releasing.