I took (and am taking this fall) a front to back one. I havent' had experience with a side by side, but I did notice that with some, adults have to kind of hunch over to steer some of them because they had to put their arms fairly far apart on the handle. It looked a little uncomfortable on the neck and back area.
The front to back ones are a little challenging to steer, they don't turn on a dime, that's for sure and I have to pick mine up from the back to get around sharp corners. That's kind of a pain. If we have to run (out of the rain or something), it's tough because of the steering.
My kids are 5 and 2 so I really get a good work out when I'm pushing them!! The front to back is a heavy stroller and my kids are getting heavier every year!!
Try both styles out in the stores, if possible and see which one you like best. I think both have positives and negatives so you'll really want one where the positives out weight the negatives in your situation.