Install xim1 to .\xim-ps3
set it up per the tutorial, there is a thread
would also suggest associating ".ps3" files with xim1 and renaming all .xim files in your xim-ps3 directory to ".ps3" so doubleclicking a ".ps3" file opens xim1, there is a thread for this, but it's entirely optional
Install XIM2 to .\xim360
set it up, per the tons of threads.
I have, or had rather, both co-existing peacefully for a couple months til I ditched my XIM1 and switched both boxes to XIM2 (using XBA+ for PS3 use).
I should mention that I did on occasion have to unplug and replug both here and there, but at no time do they just stop working altogether and require an uninstall/reinstall.