The VTF15h is more like $200 more than the XV15, because shipping is $140 on it, whereas shipping is built into the price of the XV15. The VTF15h is likely more powerful, but it is a large sub. A VTF15h in a 12x13 room would be pretty nuts, but fun.
One thing I would add, the VTF15h was found not to be bullet proof in single port mode, that means a strong enough deep frequency could cause the driver to bottom out in that setting. This is not a problem with most stuff, since most movies and music doesn't have massively boosted sub 20 hz material. However, since its pretty easy to generate a very strong low frequency when making electronic music, I would say the VTF15h should only be operated in 2 ports open mode or sealed mode if you are making electronic music, but not 1 port open mode. Unfortunately, 1 port open is where you get the deep frequency output from the VTF15h, as 2 ports open rolls off at 30 hz. On the other hand, with 2 ports open mode you would get truly massive output above 30 hz, and 99.99% of music lay in this frequency range.