We've rented a double stroller 3 times, and have used Magic Strollers, Orlando Stroller Rental, and Kingdom. Magic Strollers is a bit more expensive, but they often have availability when the others are sold out and there is a 10% off coupon in the Birnbaum Guide. OSR and Kingdom were always the exact same price for us, staying 8 nights. We had no problems with any of the companies. OSR gives you a little cooler bag, Kingdom strollers lets you borrow a cooler bag, and there wasn't one that I recall from Magic Strollers but we never used any of them. We did initially get a stroller with a broken handle from OSR, you couldn't adjust it, but I called them and they switched it out late on our first day so we only had to use the one with the handle set for tall people for one day

. Not a huge deal. They all offer free rain covers, magic Strollers says it isn't guaranteed but i called and they said they can't recall anyone ever wanting one and not getting one, and we did indeed get one. We never had to take the stroller out of a bag or put it back, it was just wheeled to us, but I have heard sometimes you do? Not sure if bell services did that for us, if it was because we rented a double, or if it's just random. Another thing I wondered about was the parent consoles for the citi mini GT doubles - the ones that fit the citi mini singles don't really work for the GT doubles but the long ones made for Bob Dualie strollers do. So I emailed all 3 of the companies. Kingdom has the long bob parent consoles, so I went with them the third time after I realized how terrible the smaller one was when we rented from OSR. OSR says they have some Bob consoles but not all, and you can request them. Magic Strollers does not use them. But this only matters for that particular stroller (Citi mini GT double) and if you really care about having the drink holder/parent console for your drinks on the handle. I also wondered about rain covers, since we have a citi mini GT double at home and the rain cover made for it seemed so nice. OSR said they manufacture their own rain covers for the baby joggers and feel that they repel water better. Magic Strollers uses baby Jogger brand rain covers. Kingdom strollers also manufacture their own rain covers based on the baby jogger pattern. The only time we had to use the rain cover was from magic Stroller, with the actual baby jogger cover (which I was pleased with), so I can't speak for the off brand ones the others use but they swear they are better
I hope that helped someone, it's probably most helpful if you want the citi mini GT double (which I like for 2 kids, with one being older and thus bigger).