ETA: I looked up the CR research and here you go:
Britax Roundabout and Evenflo Triumph 5 both got an 81. The Evenflo is $100 cheaper.
Cosco Alpha Omega got an 80 (that's the one that will last you until they are 100 pounds).
Britax Marathon got a 58 but was the most expensive out of the bunch.
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most of the faulty research from Consumer Reports was about infant seats, not convertible seats, so they are still the best place to go for safety ratings.
This will give you ease of use ratings which isn't necessary the same as safety ratings:
I second the other person who mentioned the Evenflo Triumph 5. It is just as safe as one of the Britax models (can't remember which one) and about $100 cheaper. We have the Triumph 5 and love it. Just make sure you get exactly the Evenflo Triumph 5. There are other Evenflo models that have similar names but only the Triumph 5 received super high praises.
There's another convertible car seat out there that actually goes to 100 pounds (unlike the Evenflo that only goes to 40). It's more expensive than the Evenflo, but it's the last car seat you'll need. You won't need a booster. I think it's the Cosco Alpha Omega Elite. I have a friend with twin boys and she LOVES this carseat.