overall, it's hard to beat the money based on a nitrous setup. Cam only, or even getting some cheap ported heads like patriots or something, and spraying it, was a quick and easy way to have fun.
I always look at everything though. Let's say you are gonna be working with a stock longblock.
Headers - $350 ? For the LSx swap?
Nitrous Kit - $500
Electrical stuff for nitrous kit - $200 (like window switches and WOT switch, etc..)
Misc jets, wiring, relays, etc...
So figure you'll have $1200 into all that.
OR for the turbo...
Flipped manifolds like I'm doing - $50
Tial 50mm BOV - $225
Tial 44mm Wastegate - $400
B/W S475 Turbo - $600
Piping - $100
Misc - $200
So maybe $1500??
Now these are just ROUGH ROUGH estimates and I'm sure I'm missing alot on both sides, but where I live, bottles are $5.50/lb for nitrous. So 10 bottle fills, which would be about a month with my racing schedule, that's $550 swing.
BUT, the easier thing would DEFINITELY be the nitrous.