4-man pools = just for getting the tournament done faster. No other justification, really. Seeding would be worse for subsequent pools since you only have two tiers to work with instead of three (6-person top 3 getting out vs 4-person top 2 getting out).
Basically four person pools is pointless, you might as well run a double elimination bracket. All four person pools is is faking the idea and purpose of even running pools, the idea of which was to give the player, in particular not the best players, a chance to play a lot of people in real tournament matches.
I'll never forget my pools at Melee FCD, where it was 8 person pools top 4 advance into 8 person pools top 4 advance, etc. It was awesome, I played so many different people, some from other countries, and many way better than me. I only got through to the second round, but I felt I easily got my money worth of matches.
Looking over the schedule for Apex 2012 I see some things that are worrying. Tournament match time for Brawl, for example, will be what? 3PM - 3AM? 12 hours to whittle 300 people to top 8. If the argument is there will be plenty of friendly stations, then why not just make the pools larger and take longer to complete the tournament so lower to mid level players get more matches, especially with better opponents since typically those better opponents will not be playing friendlies anyways (they will still be in the tournament!)
Don't get me wrong, first and foremost the tournament needs to be completed. But don't tell people there will be plenty of friendly setups all weekend long & that you need to run four-person pools in order to finish on time, since they are contradicting statements.
Ideally tournaments should be run in order to give the most tournament match time to as many people as possible, since right off the bat from the first round of pools no matter how you run it you will likely be eliminating half of your entrants (e.g. the majority of your paying customers). If this indeed is the goal or at least a higher priority then simply completing the tournament as fast as possible (e.g. a single elimination bracket) then it is simply a matter of looking at the number of setups available and the number of hours available. The goal is to maximize the average match count (average = # of total matches played/# of entrants).
If it is truly about creating the best experience possible for as many as possible at the event, then maximizing tournament playing time should be important. The stream monsters won't be effected at all if there is four-person or six-person pools, so that isn't even a factor here.
Also Melee finals an entire day after Melee finishes?