I think those are cool, but for me not very practical. Your older son is just kind of stuck sitting in that little seat - no shade, no recline, no foot rest. It's kind of like being in a shopping cart. I guess it depends on what you are using it for. We use it for traveling and lots of day trips - it't critical to have an easy fold w/ no extra parts and I love that my older daughter can climb in and out by herself.
Did you look at the Baby Jogger City Mini Doubles? Your son would fit in that fine, my older daughter is bigger than he is and still fits.