I've got both the Spot and the XP2. Very similar performance. Both provide plenty of light for glacier or trail navigation. Both have a decent battery life.
I use the XP2 more often because I have the rechargeable battery kit for it. Nice option - for night time trail running I can run it at full brightness regulated w/o worrying about burning up $$$ on batteries. I use it unregulated on alpine stuff and have had plenty for multi-day trips.
I'd be happy with owning either one on their own.