I'd recommend a quality latex primer followed by two coats of latex paint. It's easy to apply, and easy to clean up. If you scuff the surface, or drill holes in it on accident, or scrape it up bad, simply patch with bondo, sand, and refinish. You won't be afraid to "use" the table top. Just re-paint the top surface every other year or whenever you feel like it to keep it looking like new.
Have you ever tried to keep a varnished table top looking good? Especially one that is also a workbench? The finish will mar, scratch, and look dirty all the time. I like my table tops to look clean and heavy duty. Clear coats are just so hard to maintain in good shape when you've got tools and chemicals and tape on them.
Latex paint!