Different plane dueling is very common in the DA. So so is multi plane engagements. In fact Bat, maha, SAD1 and I (with a few others) were flying 2,2-3-3 and FFA with 109 vs spit matchup switching off....
I fly non similiar plane duels all the time and as WW said they are of real value in learning true "dueling" skills.
IMO there is no such thing as an "even" remerge. what appears as neutral to one side isn't. Best personal story on that is a series of fights I've had with Vuduk over my last few DA sessions. We've had 7 or 8 great prolonged duels that started of those "even" remerges. Unfortunately I only could convert 1 or 2 out of those to my end even when I felt I had worked up an edge. In one I just chaulked it up to a missed shot but the other 5 or more he just flew my oscar into the ground (meaning he beat me not augered me) in the end.
Now Vudak has been asking, absorbing 411 and applying stuff in the DA for awhile now and it shows. As SKYROCK said all the "even" fights are winnable...or loseable:(....you have to apply yourself to learning the subtleties of ACM to get there however....