the XT won't show it's true speed in benchmarks due to the way it uses the 4(or whatever it is)GB "SSD" for the most used files. while i still say if you want speed to go hard in the paint and get a real SSD, the XT is much faster than a scorpio black.
I haven't looked into the XT all that much so I'll take your word on it. I myself am going with a best of both worlds setup: 120GB Vertex 3 boot drive in the HD bay, and a 1TB(either Samsung or WD) 5400rpm media drive(with a 120GB mirror of the SSD) in a OWC DataDoubler.