Lucy you're right about the seat space, they are narrow. I'm thinking that in a few months Ella will be walking a lot more and I can get a buggy board to go on the back of my single Maclaren.
I'll probably keep the powertwin as I'm not sure how much I'll get for it 2nd hand and the air tyres do make it quite a light push (except uphill!), I think though that it's the tyres and the suspension that are making it tip to the side really easily. My sister was pushing it the other day, went up a kerb wrong and almost lost the whole buggy.
I like the twin techno because of the basket space, the fact the seats recline fully is a bonus and the straps look a lot better (mine are all twisted). It's lighter and the brakes are easier to apply. We have a lot of thin kerbs round here though and I'm worried that it wont fit on them, however the powertwin has wide back wheels so I don't think the techo will be that much wider iykwim.