truth is the answer is neither...the p[unch is usually landed with the fist on a \ angle too much eiother way you risk injury to the wrist....

Side hooks to the body are best thrown verticle slightly upward motion for maximum impact...the upward motion pushes the inside of the body together

the hook to the head gets maximum impact as it is coming almost back towards you...the body expends all strength into the motion then on impact the muscles maximize contraction in a chain reaction sequence that sends the power all the way up from the furthest muscle away to the end of the fist....sort of in a sonic boom type fashion.....

I wish I had video on my comp to show exactly what I mean