Haven't read much about L.A. Noire but I played Portal 2 and it is a great game, much longer/more story than the first.
So your options as I see them are take a risk on L.A. Noire possibly sucking, maybe but probably not being awesome, or have a Rick Scarf Guarantee* that Portal 2 will be tits up awesome.




*what's that asteriZZZZZZZZZZZZZZZZZZ