GEP, let's not get our wires crossed; I agree totally with your key points, namely, the degree of risk. It is absolutely safer to land and swap over (because we're all much better (hopefully!) and have received more training in landing an aeroplane than changing seats in flight).
Who's to say it's safer? We know nothing about the circumstances specifically, and it seems to me that there would be many scenarios where a swap of this sort would present no meaningful risk. On the other hand, if you look at the accident stats, the arrival, landing, take-off and departure are where most accidents happen. So who is to say that avoiding an extra landing/take-off cycle isn't safer?
Sorry to spoil the natural forum instinct to armchair-police anything of this sort.