Not the brands you're looking at, but:

My Mother's Choice double pram folds up SO small and flat! Smaller than my Mother's Choice all terrain three wheeler! Very light too (again, lighter than the single of the same brand).

Have you considered an Valco Ion Double? I just got a single one, 2nd hand, but can't say enough good things about it. The single only weighs 6kg so I assume the double would be nice and light too.