DH and I have been actively researching the sit-n-stands (Baby Trend vs. Joovy Caboose). He is a stay-at-home dad and I ended up taking the 2 kids to the zoo one day recently with one stroller and it was a nightmare - I came home saying I don't know how he has been doing it but we needed a new solution and I didn't want a traditional double stroller (too big)
So this is what we have found...
The Baby Trend is really nice, but it is bigger than the Joovy - basically as long as a single file double stroller. I found it a little difficult to manuever due to its size. It is quite heavy to lift and carry. It has a parent tray and the seat for the toddler is easy for him/her to sit on regardless of the position of the front seat. It is cheaper.
The Joovy Caboose is a bit more compact and is actually the same length as our travel system stroller, but this means that the toddler is way more cramped in the back seat when the front seat is reclined. The toddler seat does slide back and forth to try to give more room in this situation, but there are a lot of reviews that report that this moving seat is problematic. Also somewhat heavy when folded, however they do have a the Ultralight Caboose which is new for 2007 and lighter, but pricey (includes a parent tray thing which the Caboose doesn't have).
When folding both of these, the canopy has to be folded up and sticks straight out of the top making both somewhat awkward when carrying and trying to fit into a car trunk.
So, this is what we decided...we are getting the Joovy Ultralight Caboose. We figured that what we were looking for was a nice stroller for younger DS with the convenience of a spot for older DS when he needs it occasionally - sitting if possible and standing if need be (younger DS reclined in front seat). If we were wanting something for both of them to sit in all of the time, we would go with a double stroller. We are getting the Ultralight for the lighter weight and the included parent holder.
Definitely try to see both models though - we had to search and search our area for them but it was really helpful to try both out!