Series 3 = B14

Series 4? By this you mean yung N16 Sentra?

Syempre ang pinakamaganda yung pinakabago, which is the N16. All new body and engines na eh. But I don't think that will fit in a 100+k budget. Which leaves us with the B14 Sentra. Still a very good car. Just make sure it was well taken cared of.