Hi tigerwoods,
I've just switched to a Hepco&Becker topcase (45 litre Junior), after years with a Givi box (E50 Maxia).
Although I'm noticing the smaller size occasionally, the H&B is much squarer than the Givi, so a lot easier to pack.
Don't know how the H&B rack will stand up to the elements yet (only had it 3 weeks), but Givi stuff I've had previously was very badly finished - paint bubbled and flaked (just like a BMW fork brace, so at least it matched the bike!)
H&B box feels much sturdier than the Givi. Also, H&B fasteners easier to use - Givi uses a weird system which is difficult to explain to pillion, so there's no chance of them getting your sidestand plate out whilst you hold the bike up on a soggy rally field.
Slight negatives on the H&B is the number of locks - two have to be unlocked to open the case, with another one underneath the case to lock it to the rack. Don't know how long this 3rd one will function, as it gets covered in crap. Givi locks feel better - key locates itself, H&B key needs to be centred in the lock.
My Givi box (and others I've seen) all rattle on the rack. The H&B is solidly mounted to the rack.
Also consider exclusivity - Jap bikes all have Givi luggage, and you don't want to associate with those sorts, do you?
As you might have gathered, I much prefer the H&B case. I'm just about to order a pair of H&B panniers, so can give you an idea of those in a week or so.
cheers
Steve