I'd have to disagree there Zazen. In both cases you will get easy and difficult shots. Plus both shots will become easier in time, with practice.
For instance, a fairly common shot you'll get as a BnZ'er is a front-quarter "raking" shot. You dive, they break into you, you aim where they are going and shoot. Depending on how far into the turn they get, it'll vary from a straight planform to maybe halfway between a planform and a head-on. Is that a difficult shot? I don't find it particularly difficult, but I've been practicing that shot for about 2 years now.
Actually, a lot of the time in a "furball" most of your shots are not tracking shot, but snapshots. It is exceedingly rare to actually "saddle up" on one enemy in a multiplane fight. Most of the time you take your shots were you can get them, and they usually end up being 45-90 degree snapshots, just like if you were BnZing. Of course, you have slightly more time to aim in the latter situation, since your speed isn't as high, but on the other hand there are consequences for missing the shot.