The impression I get with Stop the Secondary is that, ideally, it will be a pokemon that, with each individual set, will be able to completely wall a certain group of non-damaging attacks (off the top of my head: Magic Guard Refresher/Psycho Shifter/Taunter for status, Leech Seed, etc. OR Scrappy Spinner for entry hazards OR Scarf Klutz for Trick, just as examples), not that it will be able to wall all non-damaging attacks at once. Two great abilities and 4 slot syndrome will determine which non-damaging attacks this pokemon can shut down and which ones it can't. The options are wide open. The main problem I have with it is that it is such a reactionary concept. It's trying to explore where the metagame could be, not where it could go, with the addition of this new pokemon. It's taking certain things away from the current metagame instead of propelling the current metagame forward. Anyway, that's how I see it. I understand that that's what a lot of people want to see with a CaP, which is their opinion and they should vote for this concept if they like that idea. I simply disagree.
The impression I get with Two-Sided attack is that, ideally, it will be a pokemon that can only viably play two disparate roles on a team (not just two sets), like physical attacker (Choice Band, stat-up sweeper, trapper, etc.) OR speedy support/annoyer/tank (Taunt, Screens, SubHeal, etc.) with no option for viably fulfilling other roles or both at the same time. This pokemon, as well, will rely on two amazing yet completely different abilities (read: Huge Power + Trace/Serene Grace, again, just as an example) and the stats to abuse both without being overpowered, of course, not to mention typing and everything else that could come together to balance it out. The idea that it has no true counters (but each role does) will change the team-building process of most battlers, as they must account for both versions of the pokemon when considering strategy. This concept, in my opinion, would be the more challenging of the two concepts to fully achieve, as we'd have to be very scrupulous as to not open the door for a middle-ground to slip in, which is why I think it will teach us more about the metagame during the building process, as well as in playtesting.