It is a combination of both. The boundaries and priorities are adjustable. "Searching for Guardians" looks for other players within a specific range of values to populate a pool. The value could be based on connection or skill. "Evaluating" is when the other factor is used to narrow down the pool to create a lobby. The acceptable values can be set to any range. It's my understanding that if the initial search or the follow up evaluation doesn't return enough hits the logarithm expands the range of acceptable values. That's one reason it sometimes takes so long to form a lobby. The logarithm is making multiple searches, expanding on the range of acceptable values until it gets enough hits to form a lobby. In that case with skill as a priority, some of the final inclusions may be half a world away. With skill cranked all the way to its lowest priority - the range between acceptable values is unlimited - only the first step would matter and connection would be the only value considered. Sbmm favors players who fall into the middle or slightly below levels of skill because their population is large enough that finding decent connection values within their skill range is much easier and they tend to face opponents around their own level. It sucks for higher level players because they are much fewer, making search times longer and acceptable connection value ranges much broader. Both groups tend to want what's best for them. It seems obvious that sbmm benefits the greater number of players, but over the years pvp mains have developed a litany of arguments against that assumption. But whenever most players have a choice, they tend to choose sbmm. Players could have chosen the cbmm option but didn't, the player pool dwindled. And isn't it interesting that the comp modes use sbmm but we don't hear demands for its removal there? But these things happen in cycles in Destiny so we'll see what the future holds.