batteries or brushless

if u go with lipos what does it really improve?just the run time?and are they really hard to maintain ?they said u need to watch them while charging..im thinkin about the a123 batts but the highest cells they have is 4200s 2s2p.with that power u think it can handle a savage?or im gonna need to run 2 of them ?ive read that the a123 batts are easy to charge no need to watch them while charging..so now im thinkin of getting into lipo also..but id like to know more about it too .