Isn't rule 30 also Turing complete? Therefore GoL and rule 30 can both emulate the other, modulo possible exponential blowups in time/space requirements.
No, rule 30 isn't known to be Turing complete. You're probably thinking of rule 110.
Actually, according to the extended Church-Turing thesis, all Turing complete systems can emulate each other with at most polynomial overhead, so no exponential blow-ups.
The only possible exception we know of is quantum computers.