Is your band currently recording?

Do you have other amps to use?

If your band is currently recording and you got a new toy and want to use it, I'd go with the cab simulator. If the band just started up and you want to write material I recommend going with the cab and power.
Major of 7 String Legion 7 > 6

Carvin DC747
Ibanez RG2228
Schecter Avenger Custom Shop
and my baby....
Gibson Explorer Studio