Well I jumped into this thing as a Rocket-Acclaim speed comparison, and I think the Rocket is very close--but probably only up to the low teens and probably even then only at reasonable cruise power settings. I gave it a shot yesterday at 21 gph, but only at about 8000 feet, and could only get 186 KTAS.
I have also been at 15k, 20 gph, and 199 KTAS (but not this weekend), which would be sorta close to an Acclaim, but not as fast. I think the parasite drag of the better acclaim aero starts to tell above about 165 KIAS. Beyond that I can throw more gas at it but don't get much speed. Higher I'll be faster and more efficient, but I'll always be 5-10 knots slower than the Acclaim and heading toward 15-20 knots slower above about FL 180.
They're all fast airplanes, no doubt. Some are the perfect balance of speed vs efficiency, and for that the Acclaim and the 252 or Encore will compete pretty closely. For those of us who are used to burning 1000 pph of JP8 and running at .95 mach in cruise...well, a Rocket is plenty good enough. All depends on what makes you feel good: elegant operational efficiency, or brute force and "capital efficiency", or no holds barred capital outlay and the latest, baddest mutha in the valley!
whatevery puts the smile on your face when you see the numbers!