LT1 sensor is 3" vs. the LS1 which is 3.5". The LS1 is about $10 cheaper but given that the diameter is 3.5" you will end up spending more on reducer hoses and such to get it to work with a standard 3" intake or 4" intake, not to mention the size of the air filter.
Keep a MAF, regardless of which one you use. Going speed density isn't exactly plug n' play. It takes a lot of setup and tuning.