whihc tandem / double buggy??

I have a 2 year old (far from being able to walk!!) and a 10 month old and I'm looking for a new buggy as my i candy is now too heavy. I have been told the tandems are heavy and awkward up kerbs, not a lot of room for baby sitting in the back, but side by sides are bulky and dont fit through doors? the my child sienna has poor reviews?

Can anybody offer advice please??? hardly any baby stockists offer a variety so I can try them out??

thanks..

Marie