I backpacked a bit, then started cycling to recoup from knee injuries (from hiking). With a properly fit bike, long distance cycling is easier on the body than hiking is, over the same amount of time (IMO).

Cycle touring, you can cover more distance, see more, and meet more people-should you want to. It's still at a slow enough pace, that the sites can be enjoyed. Touring in populated areas offers a lot more food choices compared to bacpacking (outback type).

Comparing European "train/bus" bacpacking, I save on transportation costs, and see a lot more. I think I get a better "feel" for a particular Country/region-and it's people, compared to just whizing from one spot to the next. It's allways easier (for me anyways) to meet people in rural areas than in an urban. In urban areas/touristy bits, hostels are great to meet & hang out with folks.

Camping gear is the same, but it's easier to carry more, should you want to. Finding official campgrounds along a route usually requires a bit of planning, a lot less so though, than while on a hike where camping at designated sites is required. Wild/free camping is about the same, dependant of course upon the area you're cycling through.

I feel cycle touring is safer than bacpacking, again dependant upon the route cycled.