I think the 967 is fantastic and the lack of rolling up is totally worth it in my opinion! I'm a 34DD and I got the medium; it flattens me right out. I find it fairly comfortable actually. I recommend this one for sure.
The only issue could potentially be going to the bathroom in it. I use a STP device but if you don't, I can't speak to its usability. I guess it's possible though, I just haven't tried it like that so it may be an issue because you can't just pull the bottom half down obviously.
I already had a medium in the 998 and went for the same size for the 967. I'm not sure if I maybe stretched the 998 because I feel like the 967 is tighter but for me in a good way, so it may be a little smaller. I find the harder part is getting the damn thing past my legs because I have footballer (soccer player) thighs - huge quads, but I do eventually get it on and once it's on it's fine, but it can be a battle.