Depends on how you use the two. But before getting into why, I'd like to make a couple of observations.

There is no need for 4 in order to get more servo power. Two provide more than enough power.
The placing of servos in the top wing is unnecessary, but if you're going to do that for 4, which is a waste of time and energy, go with 2 and rig the airplane differently. That is worthwhile for one reason (soon to be described) but unnecessary.
The airplane operates excellently with two servos. Airplane response to ailerons is almost instantaneous. There is normal battery drain. The airplane even operates very well with two that are rigged in a way that gives 3 different amounts of deflection from the 4 ailerons with any aileron movement.

If you want to do the extra work to place 4 servos in the airplane for whatever reasons, then the work of placing two, with one driving the top ailerons and the other driving the lower, isn't going to be anymore wasted than placing 4. And it will be very slightly less work.

What do you gain with 4? More accurate movement of all 4 ailerons in unison. And whatever minor gains you would pick up from having only one short pushrod for each aileron. Since the airplane works very, very well with the stock arrangement, the gains from the last sentence would seem to be of no real value. It's pretty hard to justify something that isn't needed.

But having all 4 ailerons moving the same amount from the same stick commands would be worthwhile, at least in theory, and possibly in practice (see the immediately preceeding posts about trimming out rudder roll couple). And you can get that with the original location of the two servos, but with a different rigging scheme, a scheme that actually takes no more time and possibly less to do than the mfg's method of installing the provided hardware. So why go to extra work placing the two perfectly adequate servos in different locations just to avoid a rigging scheme that you can avoid very easily another way? Beats me.

But having two servos, one top wing, one bottom wing has a benefit. It just happens to be the same benefit that better rigging will do. All 4 ailerons moving the same amount is the benefit.

And people testify that the airplane flies excellently with the original setup. So what's to gain with 4? A number of things that can be bragged about but won't show in the airplane's performance. What're the costs? Time, work, money, a heavier airplane.

Want the worthwhile gain of 4 without the costs, go with 2 and rig them so all 4 ailerons move the same amounts with any stick movements.