I've got a MB Terrain double, the older fixed wheel version, mind you they are made to last for ever. I went with a carrycot on one side for my ds1 and dd2 sat next to him. It was important to me to be able to see DS1 (premmie with aponea issues) and have him led flat, which is covered with the carrycot. It was never heavy to push, even once i loaded it up with loads of shopping and both little ones. even with fixed wheels it turns on a sixpence. If I had one complaint, it was an absolute nightmare to fit in my car (Kia C'eed) I could get it in, but had to take wheels off and they aren't quick release wheels eaither on mine.
I also own a P&T sport, great for shopping in town fits in all shops etc, however DS1 outgrew baby part quick and had to go in doubles seat underneath, no storage for anything on the buggy, got to be disassembled to fit in the car, you can't feed baby puree etc while hes sat in that bottom seat, so I had to feed one then switch them, not easy trying to juggle both, the biggest drawback is the reason I'm gonna get rid of it............ now DD2 weighs 24lbs and ds1 weighs 14lbs I can't lift the front to go up curbs, I am almost totally dependant on those slope bits, its damn heavy :(
BTW my current double, well the one I'm using at the minute is the nipper double, the fixed wheel version, after buying two quite expensive doubles I couldn't justify spending out yet more, managed to pick it up for £40, fits through all the doorways, wheels have quick release if the doorway should be too narrow, its soooooo light and it fits in my car without having to use a crowbar to get it in :)
HTH