They are solid enough, so solid that the stainless bolts seize in the oxidising aluminium stays from experience - not that it's too much of an issue as you never normally need to take the stays off the guard, but I was concerned of long term durability at that interface though, but mine were still sound after 2+ years of year round commuting.
Although aesthetic is subjective I think the Honjo/VO style is far nicer where the stays fix to the guard.
Also plastic 'p' clips in the Gilles Berthoud are not as nice as the metal ones in the Honjo/VO...
All my opinion of course though.
I have got both GB and VO on 2 bikes... I almost put the VO hardware on my current Gilles Berthoud guards on the daily bike, but decided the additional cost not worth it (have actually used the metal VO p clips at the mudguard eyelets though as I had them spare).