Safety First Go v. RSTV v. Radian v. something else

We travel quite a bit by plane, and are planning a bunch of trips for the next few years. We have thus far relied on $35 Sceneras, which we leave behind at our destination but DD has hit the weight limit and DS will soon for those. So we need to come up with a plan...either purchasing something travel friendly that will be good for many years or lugging our Radians around until the kids can use boosters.

Right now, the kids are 3 years, 9 months and 33 and 35 pounds. Our next trip is planned for 3 months from now, when they will be newly turned 4. We will be traveling both within the United States as well to Bermuda and Eastern Europe and possibly Mexico/Carribean.

I like how the Go is compact and seems easy to use. But will it work in Bermuda and Europe? I understand the RSTV can be a good choice, but will it be a huge pain to put on and take off each time. We will often have short drives, so I'm not keen to be hassling with the seats every 10 minutes for 2 kids.

We can use either CARES or seats on the plane, so I'm not worried about having the seat be usable on the plane. It seems like both the Go and RSTV can be taken as carryons.

I really like the sureride as a travel seat-its lightweight with pretry high limits.

I'd be worried about the possible lack of LATCH/ISOFIX in a random car in a random country with the Go, as it's really not easy to install with the seatbelt (and even less easy when adding a locking clip.) If it were me, I'd do the RSTVs assuming they fit and call it good; the pros outweigh the cons IMO, especially with that much travel.

I'd look at Maestros too.

I would not get the Go if you're not guaranteed you'll be able to use Latch. It's a huge PITA to install with the seatbelt and it also makes it uncomfy for the kids and the harness height drops about 3 inches. (it is a great travel seat though, we've had ours for about 4 years and primarily use it when we're flying).

I'd definitely look into the vests, I think they have some rules about needing the top tether in certain situations but I'm not sure.

Otherwise the Maestro or Sureride would be great options. The harness heights & weight limits should be plenty to last them until they can use a booster and they're nice and light weight (and no quirky installation issues).

Are rental cars in Bermuda and shuttle vans/taxis in Eastern Europe going to have shoulder belts?

It looks like I need either a shoulder belt or a top tether for the vests to work.