Is Ace, 3, 4, played as A7 or hard 18?

OK, The dealer has a 9 showing. I am dealt Ace 3. According to basic strategy I of course hit. I get a 4, which now gives me Ace, 3, 4. Now, do I hit this hand again as if I had Ace,7 against a dealer 9, or do I stand as if I had a hard 18 against a 9?

I am thinking I should hit because it is still a soft hand. But just wondering. There are other times when this situation has popped up with ither cards. Thanks.