If you use poly, and you want to renew the finish later, you'll likely need to remove all of the old poly first. One of the advantages of BLO is that it can be top-coated w/ more BLO if not let go for too long. For marine use, Cetol is popular for the same reasons, although it doesn't look as nice as a good varnish job. On the other hand, it's less work to apply and maintain.
My wife's mother built a gardening bench many decades ago (she passed in the 1970s). When I saw the bench, it was a weathered top of fir 2x3s nailed together. I belt sanded it and applied epoxy, w/ some filler in a few badly damaged spots.
To protect the epoxy, I applied poly, which has lasted some 30 years, but I keep the center of bench covered w/ tempered hardboard to reduce mechanical damage from heavy stuff. The top sits on a steel frame made of 3.5" square tubing I picked up scrap.
Your top is likely harder than fir, so you may be able to skip the hardboard if you're careful.
