hey, I got a dedicated booster over using the nauti as a booster for dd (wouldn't have for her brother... he used it as a booster once, because he wanted to and it was a short trip... his Monterey he had at the time was in the house with the cover in the wash, and he wanted to be in a highback... so I put the Radian we still had for her as a spare in her dad's car into my van and let him... he had no issues sleeping in it or anything) simply because she didn't sleep without her head flopping in it... which was fine when she was harnessed, as she wasn't uncomfortable, but would be bad in a booster.
No flack from anyone over it... but then my husband didn't say anything when I let our son ride in his sister's Nauti, or down the line, when the same washing of his seat caused him to want to ride in his sister's vivo (she wasn't going with us and he wanted to be able to lean his head to the side and be comfy)... he might have (since the seats were/are pink) if we didn't have a daughter... but then, I doubt we would have had them if we didn't have one...
I don't get what is so complicated about putting a child in the seat that works best, either.