[maxSaleen]

I see your point. The design on the right gives three times as many POINTS at which heat can be transfered (and thus contact surface area between the tubes). I'd think this would be more efficient, I just see the manufacturing process being much more expensive. Most of the rads I've seen use one long piece of Cu bent many times between the tubes. The design you propose would not be as easy to make.

Solder inefciency is a mute point here because of the fact that both designs must use some bonding mehtod. To be fair we must assume that this is not a variable in comparing the two.