hobeex1 - I not sure if Hoi would give many marks for getting your Flow Distribution tutorial done for you on a forum.
bimr - I think you need to do the Engineering Hydraulics module that hobeex1 looks like he's doing.
As rcooper says, taper the channel width, plus you can taper the channel...
For a wastewater the main differences that may effect your choice are:
1) Water Depth
2) Noise
3) Aerosol Production
4) Maintenance
5) Solids content
6) Tank Size
7) Tank Geometry
There will always be an appropriate time to use different styles of aeration, no single method is always the best...
