BB and K TEc are just Gaz or Avo, whichever supplier they can get at the time. BB was Gaz, they just changed to Avo.
Ive got both sets (on two different valvers) so I can tell you that the Gaz are incredibly harsh as standard. The springs are 200lb jobs that are far too hard for normal road use, IMHO they ruin the handling at that poundage, most of the time youre bouncing around all over the place whatever the dampers are set at. Ive a set of Gaz 180lb springs going on and that should sort it out. Gaz would be spot on for any track work though,or if you lived somewhere (not UK) with smooth decent roads.
Avos are spot on for the road, obviously harder than normal setup by a fair margin, but they feel similar to my old Koni adjustables which were superb.
Id recommend the Avos for road use, Gaz for track only, unless you specify softer springs.