IT'S ONLY A STROLLER!
Go to the store and try it out. If your kid fits in it and you can comfortably push it, buy it. If not, buy something else. If you're tall, buy one with longer handles. If you're short, buy a smaller one.
Yes, double joggers will fit on the buses, in the stores, and through the gates. And yes, the people sitting around you on whose toes you have parked will not be happy with you.
Yes, the Mac is the most popular one here. If you ask "which stroller..." followed by almost anything, Maclaren something or other be the answer, so just go to their website and pick one. They hold bigger kids, so your 6 year old will probably fit in it. Your college freshman will not. There has to be an age cutoff somewhere. Ebay is the cheapest place to buy them, and no, the rest of the world will not care if you have an '06 or '07 model.
Yes, the rental strollers are expensive. The doubles are doubly expensive. If they are too much for you, bring your own and don't rent one.
Yes, most airlines will let you gate check a stroller and have it not count as the dreaded $25.00 extra bag. Check with the airline to see if yours is the exception. Most people gate check without issue. Some people have issues. There are no guarantees in life, especially from airlines.
On any given day, this board is filled with stroller questions. Seriously people, this is not a complicated real estate purchase, you are not commiting for a lifetime, it's not going to be physically attached to you forever.
IT'S ONLY A STROLLER!