There is no simple answer because it mainly depends on a game or a device.
There is not OPL which is 100% compatible with all games.
If a game is compatible only with OPL 0.9.2, than I will have to this version not any other.
Additionally instead of OPL sometimes I have to use NHDDL + neutrino to play e.g. Splashdown or ATV Offroad Fury 4, etc.
If I have MMCE or MX4SIO I will have to use newer versions to play through this device.
When it comes to GUI, newer versions have more display options.
Also newer versions have more features like DS3\DS4 support, per game config, etc.
The plasma effect in earlier versions was cool indeed.
I wish one day we can switch fluently between Korium & Plasma.
or at least have an option to download OPL with these themes embedded: e.g. to download
OPL 3000 Korium.ELF &
OPL 3000 Plasma.ELF.
BTW OPL v0.5: