I never owned the beyers myself but I’ve used both of them before and they were really nice, the distinctions between the closed and open versions were the same as with any other closed/open models! The DTs always seemed extremely comfortable to me and it’s just a matter of coincidence/need that I never owned them. So to answer your question to the best of my abilities, if you think that you’d like to have opened cans and like your 770s, then by all means the 990s would be a great choice.