For highest safety I'd stick to a modern Class B. The welded steel body with air bags, crumble zones, tested seats and seat belts, etc. makes me think there is more protection in a crash. Plus I think it would be easier to avoid a crash in the first place.
I don't even want to think of a roll-over in a large motorhome. And the idea of a large slide room scares me even more. In a roll over accident I'd expect slideouts would probably not stay connected to remainder of coach.
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