As long as you stay under the 29" mark with a SBS, they're so much easier to steer AND you can get through doorways. Unfortunately this eliminates using a Chariot double except outdoors (so I have a Chariot AND an MBUD)... but there are some good other options too--Phil & Ted's, Valco w/ toddler seat (I just added this to my collection--works great if the smaller child is in the jump seat!), or (if you're short or have a short stride) attaching a board. Nothing beats my MBUD though--and I thought I'd hate SBS but ...when I read that Maclaren didn't make a front/back tandem because they're impossible to steer I really had to trust them--they're pretty on the ball.. The MBUD steers like I have 10lbs of kid in it at most. It's amazing. Having two kids is enough work--you shouldn't have to fight with your stroller.
-N.