After just having a nifty little, stomach turning, psi-time travel experience, *urp*, I've quickly come to the conclusion that time travel done with the body would be very hard on the body.

Psi time traveling is the more efficient way to "ride the loop". Taking R&D time and effort, and vast amounts of funding into account, at multiple levels it's more efficient.

But, yeah, the empirical nature of most of our sciences excuses such the efficiency right out of the hat.