As I said in my last post, I prefer the Varathane brand, in the outdoor version. I've tried other brands, but Varathane seems to be a little better.
Now, when and if you decide to use a water based urethane, be aware that there could be some grain raising on the initial application. That is not a problem; I just lightly sand the surface with a very fine paper after the second coat. This should be standard proceedure in any finishing process. Not necessarily after the second coat, that's just my preference. Anyway, to get a really nice finish--starting with raw wood--I usually apply about six to eight coats. As I said, I usually sand after the second coat and as needed after succeeding coats.
If this all sounds like too much trouble...well, it isn't. Any finishing job--no matter what you use is more than a single step process. The great advantage of water based urethane is that it dries so fast, so three, or more coats can be applied in one day. Cleaning brushes is simple and not messy. I just wash them out in hot soapy water.
I have applied water based urethane over tung oil, and solvent based finishes and found them to be completely compatable. Of course you still have to prep the surface, ie, sand it smooth and remove dust.