Short List
C7 warranty. LS 370z no warranty.
C7 new tech. 370z old tech.
C7 no millage on non-engine stuff. 370z has millage.
C7 suspension for track comes with it. 370z need to buy $2k+ coilovers and still aren't as good as the C7.
C7 new car smell.
Or buy a base 981 and swap in a 3.8 911S engine with warranty (Porsche gives core credit for 2.7L engines get $6k back). Mid Engine over everything.