cheaper to power; 1500wvs2000w you don't have to buy a new alt. for example
sound better(this is my opinion i heard L512s getting 1000rms@1 sealed and thought it sounded like there was a wet towel over the woofer vs the 2 12Rs i have now)
the l7s will get louder but not sound as good doing it imo.
if you want pure SPL just run the L7s ported and throw 1600rms at both of them...
for a more SQ oriented setup and a cheaper set up use the Rs sealed.