Very recently, I had both a recaro euro and a britax advocate 70 g3 (still have the advocate). I took the two seats out to my van, installed rfing and stuck my 3 yo in both, snapped photos and then put her in her radian and snapped photos. My dd had a teeny weeny bit more leg room in the euro than in the advocate. I liked the euro better ffing than the advocate because my kids had a foot rest. They could place their feet on the vehicle seat. The advocate left no seat uncovered when ffing, though. The Euro's rfing shell is several inches taller than that of the advocate. The advocate's top slot is about 16.5 ish inches. The Euro's is 18. Not sure if one had any more shoulder room than the other. My toothpick kids were squished in both, but fit widthwise. My 8 year old was slightly too tall for the advocate, but had an inch to grow taller in torso in the euro.