I went through the same comparison before I ordered my Tarptent Moment tent.
First, you have to be really careful to compare apples to apples, not to oranges or watermelons. :-) If you need hiking poles for the Vamp set-up, then you don't get to claim that the Vamp is lighter than the Moment. (I fell into that same trap originally, until a friend straightened me out.) You have to include the weight of hiking poles in the weight of the Vamp system. Sorry about that; if you need hiking poles and stakes to set up the tent system, then you have to include the hiking poles and the stakes in the tent system's weight.
Similarly, if you don't already own the required hiking poles, then you have to include the price of the required hiking poles in the total system purchase price of the Vamp system. If you will be shelling out in excess of US $100 for good ultra-lightweight carbon fiber trekking (hiking) poles, you need to include that $100+ against the Vamp's "real" purchase price.
Same argument for dedicated purpose carbon fiber poles if you don't bring the hiking poles. (My slightly-bunged-up knee insists that I bring hiking poles. I use them instead of the lengthwise ridge pole on my Moment. Please see the pictures of the hiking poles holding up the center-line tie points on the Moment earlier in this thread.)
I'm 6"2" and XXL, and the Moment is plenty roomy for me to stretch and flop around while sleeping (I toss and turn and roll around a lot while sleeping). There is lots of room under the door-side vestibule for my Gregory z55 (large frame, 65+ liters) pack, boots, cooking stuff, etc. There is also a fair amount of room inside the tent on the side away from the door.
I have been backyard testing my Moment in Colorado's sweltering 100 degree days lately, and I am getting plenty of ventilation through the Moment's open door, open ends, and raise periphery (which all has netting). While I do own a double-wall solo tent with a mesh interior, I have felt no urge to go back to my old tent and just its mesh interior for these wretchedly hot nights (backyard testing, not yet mountain testing, mountain testing may give different results).
As I can get snow in any month of the year in Colorado's mountains, snow resistance was a vital decision factor for me.