I here this comment!
To me, the difference would really be how committed the players are to posting daily. Because there are posters who say, "Yes, I can post daily" and what they really mean is "Yes, I'll not only post multiple posts daily but I'll also have my character come up with RP things to say on my own so the other characters can post multiple posts daily, too!" And, there are posters who say "I can post daily" and what they really mean is "I'll post daily during combat and in non-combat I'll only post when directly spoken to and never ever come up with my own creative thing to say."
Of course, I over-exaggerate on both extremes! But a party of six of the first type would easily be a quick moving game. A party of six of the second type or even three of each type would definately slow the game down.
But, unfortunately there is no way to know for sure until the game starts, in my own opinion. I'm sure whatever you decide will work out. Your other games don't seem to have a problem moving along - so you're obviously doing something right!
