It's nothing like that, I have tried all sorts of different export options with always the same or very similar outcome.
If you try a side by side comparison of a song made with VSTi s and a song made with soundfonts. I can vouch the one made with soundfonts will render slower. It's only a fair test if you make the song the same length and have the same amount of instruments/effects. It would be easier to do this with the song being around 2 minutes. Much easier to judge that way.
Soundfonts are sample based therefore every single sample has to be accounted for. It's the way FL reads a soundfont that makes it slow, or at least something along the lines of that.
So that is what I already know, what I was asking is if there is a way to speed it up, however I am actually done exporting and it doesn't really matter anymore. I didn't fix the issue, I just sent the .FLP to a friend.