Well, first of the lt1 is better suited for boost than the ls1. the lt1 head is a traditional SBC head with 5 head bolts per cyl. the ls1 only has 4. The LS1 make alot of power NA and on nitrous. Building an lt1 is cheaper than an LS1 for power. and Opti sparks tend to go out real quick if you rev the motor hi alot. these are all things to consider i'm sure there's more but i'm hungry and have to go eat lunch.
Check LS1 tech in the FI section alot to learn about Boosting the LS1 engine.