There's 4 scoring units in the list because of the wraithguard/ wraithblades... A lot if people are down playing the wraithblades, but without them I have no close combat in the army... Banshees have less survivability, bike units are cheap but easier to wound, same with guardians and dire avengers for that matter... They may be expensive points wise but the toughness value higher normal bolsters wound on a 5+. So a squad of 10 marines shoot 10 bolters rapid fire, that about 12 hits, wounding on 5s that's 4 wounds... I may fail 1 but they're fearless so they don't run even if I have crap rolls... And this is all dependent on me letting them get that close... I have confidence in the wraith units... Fire prism have the anti troop / tank shots, fire dragons are just awesome, the wraithfighter as long as I'm not stupid should survive the game since I can out manouver just about anything as long as I pay attention... But yeah those are my justifications for why I chose some of the units I did