Well it depends on the situation:
If I have no other choice, I'll have to deal with my crappy PC which takes about 30 minutes just to load Microsoft Word =/
But if my sister's not around, I use her exceptionally fast laptop =D
PC / Laptop and Mobile (SE X1) They are in sync though. So if I add a bookmark on my pc, it will be copied to my laptop as soon as I start Firefox on it.