Oil or Water based primer and paint over Spar Urethane

It is probably a stupid question. Which one oil or water primer and in your opinion what is the best brand.
or t n ttt for short (tnttt.com)
https://www.tnttt.com/
Micro469 wrote:Basically, when anything has to be painted, or repainted, I use oil based primer. Reason... Don't always know what the base coat is, and also it seems to "stick" better.... Better safe than sorry...