I’ve used various bags over the years. Here’s a list of some I have experience of, and my thoughts:
Mono Vertigo and M80
Very good, though quite expensive.
The M80 has more storage than the Vertigo - whether that’s good is up to you. I’d personally rather carry two bags than stuff the everything into the gig bag.
I did find the neck holder to be too narrow for wider necked instruments, I play 6 string basses - the neck sits on, rather than in the holder, which is a fixed width moulded affair.
Mono also do a much cheaper Bass Sleeve. This is fine for instruments with flat headstocks, Fender etc, it’s too shallow in my opinion for instruments with tilted back headstocks.
Protec Contego
Heavier than the Mono, also much cheaper. These though offer great protection for your instruments. They’re a hybrid design, using stiff padding rather than soft foam.
They don’t seem to have a retailer in the UK, but you can get them from Thomann. The neck brace is a better design than the Mono. It uses a Velcro strap rather than a fixed-width moulded brace.
Gruv Gear
Awful. A really silly idea, very uncomfortable, my shoulder was aching after walking less than 100 metres with the one I had. Fine if you’re travelling by car though I guess. They are quite long though, so ideal if you own a long instrument.
Reunion Blues Aero
These are really nice, I use one of the at the moment. They offer great protection for your instrument, whilst not being too heavy. The shoulder straps are easily stowed away when not in use, which is a useful feature. The neck brace is similar to that on the Protec bag, accommodating instruments with wider necks.