Well 77 as a pair has slightly better chances to win against AK, if you want to confront those two
hands. But on other hand AK could dominate such hands like AJ,AQ,KQ, which could give many chips to you with a good chances. Also AK has one blocker for each of two best premium pairs like AA & KK. So it's less likely you will face them. And it's way much easier to play AK postflop either. Either you flop it or not. With 77 it's always hard decisions.. In most cases you see an overcard on flop or even worse, two overcards and you have no idea where are you standing at. And even if flop has only rainbow small cards, you still could be way behind against higher pair and overcards like AK, AQ, AJ, KQ and many others connectors like 89, 9T, TJ, JQ do have still many outs.
Considering all these, i'm glad to steal with a hand like 77 from late position, but playing it post flop can turn to pain in ass very quickly.