I won't have a chance to do an A/B comparison for logistical reasons: I have the Oehms recording in San Jose, while the ABC Classics one is in S.F. Furthermore, I'm just not going to have the free time for a while here. So, I'll try to give you some breakdown based purely upon my memory.
Oehms makes fairly dark sounding recordings. And while the Stenz/Gurzenich M5 strikes me as being a tad smaller in scale, it's also slightly darker in timbre. Think of the sound of the Cologne Radio S.O. playing in Koln's Philharmonie, and you'll have the right tonal idea in your mind. The Gurzenich Orch. sounds very much like the radio orchestra. Since the Gurzenich one is still fresh in my mind, I can tell you that the first, third, and fifth (final) movements are outstanding on the new one. I remember liking the second movement just a tad more on the earlier one - especially the part where the low brass are wallowing around in the depths, accompanied by a series of four tam-tam strokes (just before the first sounding of the big chorale tune). For my taste, the horn solos in the third movement could be a tad bigger sounding (sounds like he or she is using an Alex.). I remember the horn solos sounding a bit bigger on the ABC one. However, the pacing of the scherzo is excellent on the Oehms one. On the new one, the Adagietto is cut down to bit less than 9 minutes. It still has plenty of rubato though. The way Stenz handles the approach to the return of the big chorale tune in the finale is just outstanding. There's no slowing down before the point where Mahler allows you to slow down. In addition to all this, Stenz has probably made me like the first movement more than anybody has. I've never been a big fan of M5/I.