The Momentum's MSRP is a little higher than $300, but with an online sale, coupon or at Razordog Deals, you might find them lower. At $300 or below, they're a worthy contender - they sound really nice. I can't compare direct to the 1R as I've yet to try that one, but I really like the sound of my Momentums. The bass is punchy, and definitely emphasised a little (but not much - they're just north of neutral to my ears), and the overall sound is quite detailed, which should do well for all kinds of rock.
Portability-wise, they are a very small headphone, but they do not fold flat. They are great around your neck, but should you need to carry them in a bag, their case is rather bulky. My bag can always fit the Momentum (the sound is worth clearing some space IMO
), but it's something to note - the case
is large, but very protective.
If you have ears of average or small size (less than 70mm, say), the Momentum's small earcups should fit you pretty well and be very comfortable. I also reckon you'll be rewarded with great sound for a closed, portable headphone at the price.