I tried out the BJCS instore with my daughter and niece who were about 8.5kg and 10kg. It was really difficult to lift up the front to go up a step and didn't feel particularly maneuverable. I thought it would only get worse with time as the babies got heavier. But it would be good if you live in a very flat area and I love the seating options on it.

We then went to another shop to try out the B-Dual on the off chance that we liked it. I had been convinced we'd love the BJCS and that the B-Dual wouldn't be right for us, but we loved the B-Dual. We've had it for 5 months so far and I still love it. It's easy to push and steer, has a huge basket, loads of seating options and spacious seats with big hoods. If it were me, I would have the toddler on top facing you, with the baby in a soft carrycot in the bottom seat, so you can see both children easily. Are you looking at the current B-Dual or the 2012 version? If you don't know, the 2012 has slightly better wheels, canvas fabrics, the harnesses detach into 5 straps (the current one has the shoulder and hip section as one strap like in a 5 point harness carseat) and I'm sure there's something else I can't remember! It does sound good, but I'm not sure it'll be worth the extra cost. At the moment you can get a B-Dual with second seat, carseat and footmuff for £300-350. The full price for that would be about £800 I think.

If you can go and have a look in real life, I'd do that, but I think the B-Dual is better and it's much cheaper at the moment. Both of them have really good resale prices though, which is nice to know.

I have had both. I loved the BJCS. It was fab - everything from the small fold, seating positions, huge basket, handbrake, large hoods etc etc. brilliant. Kerbs were never an issue for us. All was well until about 9 months when the BJCS started to feel heavy to use on our every day route - to the point where the insides of my arms hurt. I could only do two more runs after that before my arms were in agony and I ad to reluctantly admit defeat. I have a 21 month gap and two tall children. So in reality you would probably get more use than I did, but 9/10 months for us was not value for money (although the resale value was good). The B-Dual was fine at this point and later to push. I agree with aswellasyou in that there are a lot of good points to the B-Dual and it's definitely worth a good look at it. The only downside really is that the chikdren seem to 'hang' from the harness but putting the calf rest up to horizontal alleviates this.
I have tried many double pushchairs this year and crucially a double needs to be easy to push beyond the baby stage - all tandems are easy with a young toddler and newborn in! The true test is 6-12 months later as the children start to grow.