The LRP Spec 2 has fewer ports, which means (in this case...) it has more torque and slightly less on the top-end.
The Dynamite Big Red .28 is based on the Spec 2. I had and ran both at the same time, and also have a 454 (identical to the Spec 3), and they're all very similar... All very good too IMO.
If you're trying to decide between the two (assuming you can even still find a Spec 2, which must be..., what, 5+ years old?...), I'd get whichever is cheaper... All of the above would eat Savage X drivetrains alive back in the day... For a heavy XL I don't think there'd be much difference. The Big Red is very nice (for the money...) Had all of the above in LST2's... (which are heavy...)
What IS better though is the LRP ZR.30X... This engine has clearly more overall oomph, but doesn't lack on top-end. Idles and tunes better too.... I like all these SH/LRP/Nosram/Losi/Dynamite engines though... - all great budget basher MT engines...