What will sound better and hit hardest, 4 L715s or 4 sdc 2.5 10s?

it may be possible to beat him with four hdc 10's with the perfect box.the reason i say that is i am assuming he is using a sealed box. a ported box for four 15's is too large too fit in a 1985 olds 88. i would call audioque and tell them what you want to do, they may tell you will be better off with a pair of 15's or 18's .