Lol that's not considered similar specs... similar would be the Speed 18x20 and YT Prestige MP, where specs are 1,2g and 1,2 pts apart. In this case the difference would be weight distribution.
The radical is a very solid racket that does everything well- very well even... but is not outstanding at one thing. I could never play with the Rad line except for the Ti., every ball I try to rip would sail long.
The Speed 18x20 (and the line overall) can be described as a bit raw - It packs quite some power and spin, though the power is not as predictable as the Prestige. Search for the thread "Question for drakulie" and you'll see probly the best reviews on this racket.
Demo demo demo, they're very different!