Forward.
I can't think of any reason to go back. We know pretty much every there is to know about our past, whereas the future would be beyond anything we have or can ever imagined. Even a 100 years from now, it would be a completely different world. Think of the 1920s and compare it to now (keeping in mind that technological growth is exponential in most fields).
It would be great to experience the advancements in medicine, spaceflight, just technology and human thought in general.
On sidenote, there is a pretty well established conjecture in physics that it's not possible to ever go back in time. Travelling to the future on the other hand is easy (well as proof of concept, it gets hard when you want to travel fro any appreciable time). Infact we have already proven/done it.