I go back and forth between the clip main and the spearpoint main blades. I guess that is why I own more than one. I think I prefer the clip in the single blade configuration and the spear in the 2 blade jack pattern. I like them all so much that I cannot pick just one, but if I had to, it would be a two blade. I really like how the two blade TC Barlow (same pattern/body as the #15 Boy's Knife) fills out in my hand, and how the weight makes it feel just a bit more substantial or solid than the single blade version feels to me.
The single blade can't be beat for it's slimness and minimalistic feel that is provides. The single blade TC Barlow goes completely unnoticeable in my pockets, while the 2 blade jack's presence in my pocket is more than obvious.