I find xJournal to have more features and generally be stabler than iJournal. iJournal will freeze up and crash (sometimes the whole computer will crash with it) if it can't log into the LJ servers; xJournal allows for off-line writing and saving and such, and has a great interface for managing your friends groups.

Also I think the whole setup and general feel of xJournal is nicer.

So that's my vote.

And woo, powerbook!