You might wonder what the difference is as they both have water in the name. My understanding is this, a polyacrylic is just like a can of paint but without any colorant in it at all. So when it dries it is clear but not any harder or better than regular acrylic paint ( regardless of what the can says ). A waterborne urethane is achieved by first dissolving the urethane in alcohol then using water to carry the urethane. Once the water dries you are left with a urethane finish which is way harder and nicer than an acrylic finish. Oil urethanes will yellow over time but waterborne will not.
The product I use to clear coat my kitchen cabinets jobs is made by Varathane and here is a picture of the can. It is actually made to use on floors so using it for cabinets makes for really strong protection.
You might be thinking, "Why clear coat the cabinets in the first place. Just use a good paint or an oil based paint and be done with it." Well here is the answer. If you where to paint your kitchen cabinets and give them the best paint job possible when family and friends saw them they would naturally want to touch them. Then they would say, "Man, you did a great job painting your kitchen cabinets." But when you use a good clear coat like the one I use when family and friends touch them they say, "Wow, you bought new cabinets." It's that big of a difference in look and feel and just as big a difference in performance too.
The first three photos show the cabinets before I got there. The homeowners wanted them a darker warm gray. Plus the existing paint job because it was sealed with a polyacrylic had gotten dirty and chipped.
Look at the left side of the cabinets and you can see the dirty marks and chipping.
I usually take off the doors to prep them and paint them. This island had been painted twice before and showed it. Instead of trying to sand them down I used a stiff scraper and was able to scrape off all the previous paint and get it down to the original white color. The island was painted with a latex or acrylic paint before but never primed and that is why I could scrape it off. If it had been primed before painting I do not think I could have scraped off the paint.
It was big mess to get the paint off but worth the effort. After I scraped the paint off I sanded the cabinets lightly with a 220 grit and they came out smooth as can be.
You can see the texture here in this next photo that was on the island cabinets. This got this way because of the application of the paint and clear sealer. Once I got all the paint off and sanded they were really smooth.
The next four photos show the completed project. The new dark color goes really great with the countertops and backsplash.