I actually have an M80, M80 double, the Protec Contego and the Mono Sleeve.
Apart from the ridiculous buckle and flap I actually prefer it over the Contego if I do not need to take too much stuff with me as it is light but does a good job at protecting my bass. I carry my strap, mic, couple of leads and bass comfortably.
M80s still are the best option if you need to carry more imo. Contego for sure is a good bag/case, but not an M80.