Furniture, Wood and Cabinetry Finishing - refinishing tabletop with polyurethane

I have stripped a mahogany table, and I want to refinish it with varnish or polyurethane. I have heard that polyurethane is too brittle for tabletops and can crack if a utensil is dropped on it. I could not fine any varnish especially formulated for tabletops in the store. Is polyurethane OK? Also, the original table had a dark patina. It looks like this will be gone after sanding. Should I stain the mahogany to make it darker? I imagine that this is just a matter of taste.

Sandy,
The polyurethane will be fine for a table top. I've done numerous items including my family room coffee table; it accepts hot coffee cups and sweaty beer cans with no problem, anything wipes right up. As to the brittle question - haven't heard that but the wood may stll acquire a dent if something is dropped on it.
If you need to sand the table, it probably will require a stain of your choice.
Some additional tips on the poly. If you thin it with mineral spirits it will go on smoother and leave less tiny air bubbles. Between coats sand lightly with 400 grit paper, wipe with tack rag and apply any additional coats.
In some casea I've thinned it to 50/50, but it will require more coats though.
fred