US Airways has a 50% bonus on points transferred from spg. However, it can take some time for the miles to post and it's a risk when looking for availability. MR points post instantly (most of the time) so if you find availability you can book the tickets. You would probably want to use the MR for flights so you can use your *points for hotels.
What type of hotel are you looking at?
Category 1: 2,000 points weekends, 3,000 points weekdays.
Category 2: 3,000 points weekends, 4,000 points weekdays.
Category 3: 7,000 points, 5th night free.
Category 4: 10,000 points, 5th night free.
Category 5: 12,000 points, 5th night free.
Category 6: 20,000 points, 5th night free.
Category 7: 30,000 points, 5th night free.