Have been to Atlantic City a million times and Vegas like a dozen times. Vegas is way better, but Atlantic City is trying to catch up. Check out the new tower at the Borgata. No gambling but lots a pampering and such.
Vegas has better clubs, but you can't get into them anyway.
Atlantic City cannot compare to Vegas, period. Vegas is 24/7 and Atlantic City is not. But you are only 18 and you cannot enjoy the activities of drinking and gambling, so why not pick another city until you are 21.
That's a tough one.. I've kinda always wanted to go to Vegas.. But Atlantic city looks fun too... I dunno..
I'd say for you Atlantic City since you've been to Vegas 7 times.. You might like Atlantic City better, never know..