I suppose that one difference is that the facts on what happened in the second incident are less easy to come by. UPI reported that the US raid 'penetrated more than 25 miles into' Syria but the closest thing to major media to pick up that story seems to have been the Washington Times. It's clear that the US forces shot at Syrian troops and wounded or killed some of them, then held them for a few days before finally returning them. It's possible therefore that the second incident did not in fact involve a violation of Syrian territory if (and only if) the Syrians were on the wrong side of the border. It's odd though, that if they were the US didn't make more of that violation at the time. Then again, the Syrians clearly decided not to press the issue either once their people were returned.
Note that by asking this question about possible equivalence I'm not trying to suggest that if one is OK, it follows the other must be, but rather the opposite.