per gallon costs. I believe both of these are water based. Which should I use?

going over a resanded old oak floor.

A two part finish will be more resistant to household chemicals. This type of finish can cost over $100 per gallon.
No matter which you choose be sure to follow directions about preparation and how many coats are required. Water-based finishes need more coats of finish to provide a longer lasting wear layer. Since water-based finishes produce such a light color, I like the ambering sealer to give the floor a richer color, for the first coat. If color is important, open the gallon carefully and try a couple of coats in a small area before coating the whole floor.
Your investment of work and time should have the best finish that you can afford.
The cheaper finish may have more acrylic resin, which is softer than poly-urethane, and can gum up sand paper when you need to refinish.