Orange or Donkey ???

[mooglycrunch]

I need some advice on double prams. We have the choice of a Bugaboo Donkey Duo ( second hand, great condition) or an ICandy Orange (ex display with a discount that makes it about £150 more than the Donkey)
Can't decide between them, things we have to consider are:

I have a 1 month old and a 2.3 year old who isn't quite old enough to walk all the the time (and decides to do the floppy legged refusal at random moments).
I also have back problems which means the sling will be out of use for the 1 month old soon.
We have a small car -Toyota Yaris with a roof box

Any opinions on which is best?