lately AH has been virtually empty on euro times so i've done more DCS. Always 4YA WWII server, flying P51, 109 and sometimes 190s.
As violator pointed out, keeping sight is a must, unlike in AH you can separate from the fight in slower fighter if other guy losses sight. In AH it is quite deterministic, everyone has been flying for 10 years+, you can keep SA on cons approaching you from 5k out, there aren't any surprises if you have a reasonable SA. I'm sure we all had this "if i do this, i know i'm going to die" thought, because with 5k icons, you ain't running away if you fly something slower.
DCS icons are different. Well, there aren't any

. I'm not saying better, but different. I even TKed someone recently, he was flying a pony passing profile shot, i mistook him for dora. First bullet hit the head
It is hard to tell the enemy from friendly. If you look around to keep SA up, it comes at the cost of reaquisiton of previous contact, which isn't easy. It keeps me terrified whole time i fly, and i must say i missed that. AH did become like predictable chess at times.
Still love both games, but euro times are pretty graveyard now