Pros: Superb headphones with balanced sound and good PRAT
Cons: Cable is a little annoying and it's not the best looking
The Momentum Over Ear's and T51p's I thought were both very very good and also very similar. Both had in my opinion a very balanced sound. I did however think the T51p's had very slightly better Base and PRAT and very slightly recessed vocals but I mean very slightly compared to the Momentum's. Putting the volume up a little seemed to solve my perception of this. I also found the soundstage on the T51p's very good but not quite as good as the Momentum's. Perhaps I have bigger ears than average but the positioning of the Momentum's really affected the Base. I had to have them sitting on the edges of the back of my ears for them to sound good otherwise the base impact was lost. The T51p's were in my opinion not fussy with placement and were really comfortable too. They didn't hurt my ears and didn't clamp too hard at all. If anything maybe not enough but it didn't cause me concern because I wouldn't be running in them!
The inline controls are useful on the Momentum's and the cable coming out from one side meant that the cable stayed tidy. I found the T51p cable a little annoying. It seemed to tangle itself up a little and twist easily when wearing them.
At this point I'm not sure if I'm keeping the Momentum's or T51p's. I would say that if the Momentum's fit you will and the base impact is good for you, they are the better buy and look better too. For me though, the fitting issue is cause for concern and I really like the rhythmic qualities of the T51p's. Will see.
Sorry for the long review. First review I've ever written on anything! Hope it's helpful though.