There is no comparison. A quick search about Pinnacle: https://www.reddit.com/r/sportsbook/comments/kek5t8/warning_...
My experience (though I have never bet on these platforms) is that Pinnacle-like platforms almost never let you withdraw your "earnings". They are essentially a bookie.
Polymarket on the other hand, is just an exchange. And they use Defi to make sure you can always withdraw your bounty even if you get "front-end" banned from their platform.
So to affirm the previous poster: These companies are not in the same business.
They absolutely let you withdraw earnings. I place around 20 wagers a day. Pinnacle and Circa are used as measures of what the market is actually pricing in. You can devig lines to arrive at event likelihoods. From there you can line shop such that your expected value is positive over the long run.