Originally Posted by
stut
They are pretty much equivalent in terms of comfort, IMO.
Brussels is a decent little airport and easy to transfer at, so that's a positive for Brussels Airline.
Frankfurt is a nightmare to transfer at, but Munich is very good, so that could be bad or good for Lufthansa.
Are Swiss or Austrian options?
Funny, I've had the exact opposite experience as you (FRA A to Z is very easy but BRU A to B is a mess). But the issue is at FRA if you have to go to a terminal other than A or Z, then it is a mess I suppose. Still YMMV.
Anyways, if Swiss is an option for the original poster, that is the one I'd second.