I have the signo g2 and the blvd70. I like them both for different reasons.
They take up about the same amount of room when rf in my cars. We drive a tiny subaru (outback sport) and a tiny honda (fit) and either seat works in either car.
The blvd70 does have a little bit more legroom, but I find that the amount of legroom rf depends a lot on the shape of the backseat and whether or not it reclines so ymmv.
The recaro sits up higher on its base and has only two recline settings whereas the blvd 70 has three. The blvd 70 has a shorter shell by quite a bit, so if you can deal with the recaro lack of legroom then you would get longer rf.
The wing/harness mechanisms are a little bit different for each, the recaro has the knob on the side and the blvd70 has the button on the top. I prefer the recaro system where the headrest is truly infinitely adjustable over the blvd70's several different headrest settings.