Personally MR.
Not sure why people still value UR more than MR, if it was before the devaluation, I understand, UA was my favorite currency as well, but now besides Hyatt I see MR with much more opportunities, first of all, ALMOST each and every UA operated flight which is available for award can be booked with MR which transfers to Aeroplan and SQ for a far better value -
Domestic US/Canada flights - UA 12.5K with close in fee; Aeroplan 12.5k with NO close in fee.
NA-Europe on LO, SN, LX - UA 70K with close in fee; Aeroplan 45/52k with no close in fee.
NA-TLV on UA - UA 70K with close in fee; SQ 57.5k with no close in fee.
Same goes for intra-Europe and Europe-Middle east flights.
Now with MR you have AZ, FB, and some other partners that UR does not offer and you can find some really sweet spots when redeeming FB (and AZ) as well as all the other partners.
I value my MR points more than my UR points.