4>2>1 Vs 4>1 and Twin Scroll Turbo Manifolds

[Crucible]

Ive asked a couple of people about these but dont really get a confident answer, Is there any advantages disadvantages between the two?.

Im guessing the 4>2>1 manifold would help spooling as it would create more velocity before reaching the turbine???, but then the 4>1 mani would have more heat/energy closer to the turbine...Or would it???

Also what is the theory behind using split pulse Manifolds on s/pulse Turbos?. They keep Numbers 1 & 4 seperate from 2 & 3 and split the flange also....Bazz said its for better pulsing and Spooling.....How????.
Has it got something to do with the firing order causing balanced pulsing on either side ie 1,3,4,2 or what??

Just trying to get it clear in my head.........Which aint easy
Any theorys????

TNT