Join Date: Dec 2006
Bikes: Homemade mixte, track, commuter and road, Ryffranck road
Yes Spirit & Life are a bit stronger than Zona, thus they can be drawn thinner. Durability is dependent on who is doing the welding/brazing and what the rider does, but yes a thicker & stiffer tube is usually better in that regard.
If the frame is lugged, then you are probably stuck with the "spririt for lugs"; it's the only set with long enough butts.
As for the differences between the tube sets, weight is one, but so is tube diameter, wall thickness & butt lenghts. Never heard of Spirit Keirin.