I'm still trying to accept that no power armor is all that much better than Reilly's Ranger armor in damage reduction. Looks wise, hellfire. For my small arms character, I don't think I'll ever use power armor over Reilly's suit.
The downside is that you can't get eugene and the armor unless a ranger dies. Also I am willing to bet that power armor has a higher armor health so it wears down slower. Also power armor gives rad resistance.
I pretty much always go for the Winterized T-51B because although it has a little less DR than a regular T-51B, it has crazy high armor health so it doesn't really wear out. So it keeps it's DR high all the time, where a regular T-51B wears down and offers less protection.
Looks wise though I like the Tesla Armor or the Hellfire Armor.