If you know for an absolute fact that all shots will be within 150 yards then the 30-30 will be all you need. But if a longer shot is even a possibility I'd go with the 243. I wouldn't want to try and stretch a 30-30 much past 150 yards. I am quite comfortable out to 300 yards with a .243 on deer.

Oh yeah, as for which will put them down faster? I think inside 150 yards its a wash. I wouldn't say one would assure lightening bolt kills any more often than the other.