Moment as a commuter?
I own a Moment and have ridden a 575. My moment is built pretty light at 28 pounds. I feel I made a miscalculation in my choice of fork, however, and am planning to beef up in this area (exchanging a Marz Marathon for an All Mountain 1). This will add weight, but will really open the bike up for more of what it's great at: riding downhill.
The Moment climbs very, very well... for a 5" travel bike. Mine is built not with the RP3 but with Fox's "Ellsworth Custom Tune" shock, which is acceptably bob free. Most bobbing is a fork issue. For long road sections I use the lockout. Sitting and spinning = very very little rear-end bob. Hammering out of saddle = a small amount of bob, no big deal.
I can't see doing a lot of commuting on a Moment, honestly. It's not so much about the frame, forks, and shock as it is about the tires. You can lock forks and shock - but the kind of tires that'll open the Moment to its strengths aren't going to be very pleasant commuting tires. You're going to want something sticky and knobby for the dirt and rocks that feed the Moment's ravenous appetite. I'm running Kenda Nevegals, which do pretty well in the dirt and are horribly inefficient and very short-lived on the road. As an earlier poster noted, perhaps two sets of wheels would solve this problem.
As for the 575, I demoed it for a day on my favorite trail, a very familiar combination of fireroad and singletrack climbs, with screaming fast, bumpy, mildly rocky downhill singletrack. The 575 ripped. I loved it. I couldn't believe how fast I was screaming downhill, on a bike that handled like an XC racer. Climbing, I had to use some degree of Propedal on the RP3 to shut off the bob, but in full Propedal I could stand and hammer and the rear end pretty much ignored me, while still reacting to rocks. In full plush mode the 575 simply flew down the hill. It soaked up everything the trail threw at it. I took a four foot drop to transition cleanly; that was about the max I'd want to drop on the 575. I was impressed, to say the least. Total build weight of my demo bike was slightly heavier than my Moment, but according to both manufacturer's specs the 575 is TWO POUNDS lighter, which would make for a 26-27 pound 5" travel bike if built light.
At the time I demoed the 575, I'd had the Moment for about two weeks and wasn't really high on it. It felt heavy, long, and sluggish, whereas the 575 rode like an XC bike, which felt familiar. Subsequently, I've learned to ride the Moment the way I think the Moment wants to be ridden, and every time I come away totally charged up. It's an incredible machine. It tackles all the rock gardens and drops and rippin' bumpy downhills I can throw at it, climbs very well, jumps well, and is generally extremely plush and refined. But it wants bigness. It wants more than just trail, it wants TRAIL. The 120mm fork I've got on it simply begs to be replaced (and will be soon, oh yes, I swear it!).
If commuting is a major factor, I'd recommend the 575. It's lighter and snappier. It'll handle most trail conditions. Five foot drops...? There's a thread about this in the Yeti Forum, maybe you've already checked it out.
If serious trail riding is where your heart really lies, there's no doubt the Moment can handle more extreme terrain.
Either way, you're going to be stoked!