As far as I can see, and from the comparisons online, both feed at the same angle. The anit-tilt followers look identical in shape, but are different on the edges to fit the M2 or M3 body's internal grooves.
I did see that the over-travel insertion stop was added. Some mags, including GI, can go into the magwell too far. That could be the difference in the angle when feeding you mentioned. An over-inserted mag would feed against the top of the barrel extension/chamber. That might cause some damage as the steel tips would not be centered while it's chambered.
The M3 also has a straighter top section (less curved than M2), which makes it compatible with non-M4 standard rifles. There's a narrower floor plate/butt end on the M3 that fits tight carriers more easily. And there's a "pixeled" area at the bottom of the M3 on each side for labeling.
They also learned from users of the M2 they often loaded 28 rounds versus the 30 max. This gave them better success when loading a mag on a closed bolt. A full mag sometimes resisted insertion to the locked position on closed bolts. So, the M3 added the ability to almost insert 31 rounds. Depending on mag and ammo size variances, you may actually be able to get the 31st round inserted without jamming it in. But, with 30 rounds, it's supposed to be better able to reload a full mag on a closed bolt.
Other than the dust cover not coming standard on the M3, those are the highlights I can see/find.
Some people report empty M3's don't drop without assistance in certain rifles. You'll have to take a sample of each and test on your own guns. Most people who have no drop issues prefer the M3s over M2s due to the added features and increased compatibility.
Don't know if that answered the specific question, but it might help narrow things down if you see something more detailed.
