I have one of each.
Special: CMP wood, new Criterion Match barrel, everything is refinished. Very tight. It's like a "new gun."
Service Grade: USGI wood, original finish, 1940s barrel. What you would expect from a "milsurp."
It depends on if you're looking for something to do precision/matches with, or for the history. If I could pick one, I'd choose my Service Grade, as it feels much more authentic. This is not to say my Service Grade can't shoot--it's plenty accurate. But if you're one of the types that might not like their rifle to shoot 2-3 MOA, have some wear/character marks, then maybe get the special.
Or, if you're one of the types that tries to "improve" milsurps by refinishing them or swapping parts and stuff, just get the special.