I have both Mono M80 and Portabag. The Portabag is definitely stronger, the sides don't give and it could take more direct weight if something was stacked on it. Also has more storage then the Mono, however it is heavier by a few lbs. If you walk a distance you can definitely feel the weight difference while strapped to your back. The Mono isn't as stiff and a bit more flexible, lighter weight (as I mentioned) and water resist which is a big plus for me. I've been caught in the rain on a few occasions and the water just beads off the case. One of the things I really dislike about the Mono is that the upper carrying handle is on the backside of the case. Most of the time I have my bass standing up against the front passenger seat and there is nothing to grab onto when putting it in and pulling it out of the vehicle. (they made it that way in case you wanted to add the tick bag) which I don't. To sum it up for local gigs I use the Mono case because of the water resistance and lighter weight. When I travel or if it's packed in with other gear I use the Portabag. IMO the Portabag offers more protection (it's just a sturdier bag) Both hold the bass very securely and the zippers on both are of excellent quality.....Hope this helps!