Question for my frequent traveling mamas!

Do you think it makes more sense to get a whole separate car seat specifically for travel and a small pocket stroller like the Delta, or get the all in one Doona Stroller?

We fly for free so we often will be on flights. Car seats and strollers are checked for free, but I still am just wondering what’s always going to be easiest when airport traveling?

The Doona does seem like an infant stroller I believe, so I’m not sure how long we’d get use out of it. Opinions or has anyone used these?