I have the Muddy Hunter stand, and it weighs in at 12.5lbs, and has a 24x34 platform with a 3" padded seat, and the ability to hang in a tree that isn't straight due to it's leveling system, plus it comes with a footrest. It's the most comfortable hang-on stand I have ever used that doesn't have a sling-style seat with a back on it. I picked mine up from Muddy for $200
The Millennium is hands down the most comfortable stand I have ever used, but can be difficult to hang at times due to it's size. The platform measures 20x30 and it weighs in at 14lbs. I picked this up at the Expo for $180, but the cheapest I've seen anywhere else is $200.
Both stands pack well, but the Muddy edges out the Millennium if I'm headed to a spot where I haven't already picked a tree, due to the leveling capabilities. If I'm going to a place I been, and I know the tree is good and straight where I wanna hang, I will take the Millennium. Another thing with the Millennium is it has a wide back to it at 20", which can make it difficult to shoot behind you if you are in a small tree, not to mention the stand sticks out like a sore thumb being so wide up top. Your best bet with the Millennium is to hang in a larger tree where you don't have lots of bends and knots. One spot where Millennium edges out the Muddy stand is due to the fact that it has a reciever which you hang first, then slide the treestand into. You don't have to fight trying to hold a stand in place while you hook the chain or straps up. You set the receiver, then pull the stand up and slide it into place. I did however make a slight addition to my Muddy stand so I can do the same thing with a LW EZ Hang Hook.
Both stands are great IMO, but one may be better than the other for certain situations. That's why I have both!