Length of nose doesn't matter, it's down to personal choice. I prefer the Greenguard muzzle. It's the most expensive but once it is fitted correctly, & using their head collar makes fitting easier, it works really well. Many of the other muzzles people adapt by cutting larger homes in them, adding padding to prevent rubbing etc. If you have to do that then it must be a poor design to start with.
As I say Greenguard are good but you must take a little time to fit it correctly, then you won't have any problems with it.
I would say greenguard - we have a couple and use them on our ponies when they're getting a bit tubby - great inventions and a better fit than lots of others.
In my experience the green guard ones are too small for large noses!
I've had a shires one for years and its never rubbed; at about £15 you can afford to replace it if it breaks.
I've just started using Derby House's own brand muzzle which has a padded headpiece and throat lash and so far hasn't rubbed. The only thing is the hole is quite small so it took Jenny quite a while to get the hang of it.
I tryed a greenguard muzzle for my shetland, it was a waste of money for me as he could easily get it off no matter how tight or loose i put it! The one that works for him is the shires muzzle. I cut a couple of extra holes in his as i leave it on him for 10-12 hours. It only cost around £12 to buy. I think it really depends on what works best for your horse. In an ideal world i would prefer to use the greenguard muzzle though. I'd recommend trying to borrow one or get one cheaply off ebay before shelling out all that money for something that might not suit your horse.