^ You may find some instances of older versions working better for some games but in general the latest version is your first stop. its just always going to be the case that fixes for one one thing, may break another, so you have to experiment if you find a certain title isn't running aswell as you hoped, or had heard it can. You can run two copies but as they all create the same named PCSX appdata folder, you'll need to put them on different cards i.e SD1 and SD2 and perhaps put one in the pandora/menu and the other on the pandora/desktop on the other card. r9 lists itself as r9 in the menu but I think all prior versions just listed themselves as pcsxReArmed, so you cant tell them apart if they are both in the menu. You can also rename the older versions appdata folders and if you re-use an older version of the emu, just rename the appropriate folder correctly to re-use its settings etc at the time and then change the name again after.