Hope you enjoy them, I know I am
That's a tough one to say. $40 is a lot and the Sennheisers are likely very good sounding and the warranty is nice to have. I suspect the difference in sound is able to be tweaked via EQ so won't have to be the deciding factor.
The addition of ANC if not important to you is just an added expense. The only other big difference is the Senn have no water proofing while the AZ70 are IPX4 rated so can take lite rain and sweat. But not sure if that important for you or not. If not I am sure the Senns will be good. I know I enjoyed my MTW alot until they died.
Truth be told my MTW issues soured me a bit on trying Sennheiser again. But I am sure they learned their lessons from that 1st gen product. My MTW had the notorious battery issue so they were always dead when I wanted to use them, the case broke at the hinge, and with 2 years of light use they suddenly stopped charging all issue which annoy the heck out of me considering I paid $300+ for them.