Facebook all the way. Never used myspace, had a look at some guys pages but they seemed really messy and all over the place so never bothered.
Even I prefer FB Am using Myspace too! But I dont think FB can be substituted! FB may be enhanced! But not substituted!
For most purposes, Myspace is dead as a social network. The number of new signups on that site has dropped significantly in recent years. It's really not worth the effort to promote your site there. Plus, Facebook has much more powerful tools for app development and advertisement than Myspace does.
Myspace is very very 2005 or so. I personally would not spend my time there if I were trying to improve my followers and social media presence. Look at the social media badges on any popular site and I doubt you will find Myspace listed there. Myspace may still have a productive purpose but I'm not aware that it fits into the social networking scene in any large way any longer.
P prefer to use Facebook over myspace because Facbook has more user base than Myspace. it is the best social networking site in the recent time.