Here's a website with a wealth of information on tile.
They have a calculator (deflecto) that will tell you whether your
structure (joists, subfloor, etc.) can adequately support ceramic or
natural stone. If there is too much deflection on the floor you may
have to tear down to the joists and beef things up. This might help
you make the tile vs. vinyl decision.
Vinyl is easier, cheaper, requires less maintenance, but won't last as
long as ceramic. If you're going to be in the house for the long haul
I'd seriously consider tile. Either one (done right) will give you a
functional bathroom floor. The guys who moderate the website (most are
tile pros) will even walk you through your project. I got enough
information just by lurking.
There is a fairly wide range of opinions, even among professionals,
about what constitutes "best practices" in the laying of tile. I'm a
pretty handy guy, but I discovered I don't really like working with