My biggest gripe on gameplay is the "unlimited life" aspect of all the arenas. It turns them mostly into low alt furball fighting. I tried it in AW, WB, and AH, and I am so done now with MA's of any kind. I fly there once in a while with a squaddie for "the heck of it" but my hearts not in it. Its just not that interesting.
The thing I like most about events is the 1 life per frame or, in the case of the CAP event, 1 life per 30 minutes. Pilots grab alt because they realise they dont get free lives if they blow the first one. To me, it makes a huge difference. There is a point to it all, and its the only place to get a decent "WW2" mission. You actually see bombers and escorts, that care wether they come back or not at the end of it.
Also I find there is a completely different community amongst the regular event flyers, its smaller, and more friendly. I found this in WB too in comparing MA to event play, big time.
Im not knocking MA, it will always pay the HTCs bills, so I can fly in the Snapshots and TODs. Each to their own.
A quick edit: I also think that there are issues of balance in events, true, but they are on a completely different order of magnitude to MA. I fly all the events, some work out ok, some dont but on the balalnce, they are still far and away the best flying.