All three brands (and Deda too for that matter) make good tubes. The metallurgy is different between them, but you probably will not notice much difference. The stainless tubes made for bikes are also the lightest, strength is about the same. Some people clear coat it, otherwise you have to keep it clean.

Lugs do not add significantly to the stiffness or strength of a frame.

The nice thing about having the seat collar built into the frame is that you don't have to find a seat collar that fits. Someone I know recently went through that exercise for an ebay frame and it ended up costing him $