After much deliberation over hard vs soft luggage I decided to go with the Lomo panniers, hoping that they would give a slightly narrower setup. Actual width when fitted is around 900mm, so slightly less than the handlebars which is reassuring in traffic. It will of course depend on the choice of pannier frames, which are definitely needed.
The bags seem very well made, we’ve yet to use them for a fully loaded trip but I’m confident that they’ll be fine. Fitting and removal is certainly more involved than with hard cases, but for me it’s not an issue.
The point about security is a valid one, I’ll have to live with that and try to minimise the risk. As always it’s a compromise between size, weight, cost, aesthetics, security etc.