pretty big difference in the stiffness between custom V and the T7, and a different camber shape. T7 is traditional camber, custom V is a V rocker.
if you are looking for a really stiff board for flying on groomers Custom X and T7 both fit the bill. mind you, if you have big feet (10/11+) you will have difficulty fitting onto a T7, which has no wide version. custom X on the other hand does have a wide version.
since you haven't owned a Burton before i assume you have no EST bindings. this is binding technology specific to Burton boards - both the T7 and Custom X come only with EST technology so you will need new bindings as well. something stiff and responsive like the C60 or CO2 (both top end and both expensive) at a push maybe the Cartels. either way, it wont be cheap buying into Burton
as an alternative, i would suggest Ride Society or, slightly more expensive, Nitro Blacklight or Nitro Prolight. all stiff, all directional, all traditional camber. good luck!