I think you'll be happy with taking the smaller stroller. Just risking damage to the favorite would be enough to leave it safely at home, and you will be required to fold a heavy stroller down and get it through security, while holding your infant, and trying to watch all your belonging. Go with the easy one.
I've flown by myself internationally with babies almost a dozen times now, with 1-3 children as well (only once with all four and I almost died). At this point I take cheap and easy, and gate-check things that I would not be sad to lose.
You want to be able to enjoy your trip, and not worry about having a broken stroller to deal with that you could not easily replace.
I don't know if you will be needing a car seat, but I've used this before and checked it in a bag along with the car seat. It's actually easier to steer than umbrella strollers, and I used it for almost a week in Hawaii once. Best travel item I've ever purchased :-)