It all depends on his tune. He have a stock trans? If so, he doesnt have a wicked tune. If he haas a built tranny, then he might be packin.
Now as far as which is better, propane or nitrous...nitrous is. Ive NEVER seen propane add 400hp. You cant get the same power from propane as you can with nitrous. To a point, yea, but you get higher doses you wont. My chemistry is a little (ok, ALOT) rusty...
Look at it this way: if propane was better, well then Gale Banks would be spraying a whole crap-load in his S10 dragster. But he isnt. Hes spraying a crap-load of nitrous...