P7's can be brighter but they require more voltage/power, which means they really need less usual batteries to get the advantage from the P7 emitter. I think people have become more accepting of using less usual battery types. One reason prefer AA flashlights is that they already have the rechargeable AA batteries (which they can also use for other purposes).

The advantage of the 2xAA flashlights is reasonable output for a common battery type along with a small size and a reasonable cost. If you want more light or better runtimes, you have to give up some of the other stuff. The 2xAA flashlights can also be used off of the bike.

If you intend to ride at night frequently, the AA flashlight approach might not make too much sense.

The $100 Magicshine doesn't cost that much more than the $60 Fenix. And, ignoring reliability issues, provides more light with better runtimes.

Part of your problem is that you are trying to optimize a small amount of money (eg, about $50-100). It's hard to say whether that's a good use of your time. It's easier to say that it isn't likely to be a good use of other people's time. That is, people here might not be too interested in spending a lot of effort to save you a couple of bucks.

Other manufacturers have passed them by (I think).