The only real difference most experienced drivers have told me between std and turbo plugs is :

Turbo has definately a bit more power but that could be as Mark said from lower compression having more top end.
Dont have the hassle of thw washer falling of teh plug when making a quick change ina heat or final.

Only negative i have been told and experienced in a sense is with turbo plugs the tune seems to have a smaller window compared to std ,if that makes sense.They just seem to need a bit more precise tuning.