What would be your choice,watercolor,or oil painting??????  

Probably, oil painting over watercolor painting. Why? This is simple. Both the names are telling to you their meaning. So I think, if I put watercolor over oil, I will get nothing, because the water won't "stick" on the oil. Maybe the same will happen if I put oil painting over watercolor painting. So, I am just guessing, I had never tried.

Sorry for my last comment. I just wanna ask you, you want to put oil painting over watercolor painting or vice versa, or your asking watercolor or oil painting?

I think it would entirely depend on the subject matter, some delicate landscapes lend themselevs to watercolour rather more than they do to oil, whearas the long open time on the oil paints allows an artist to capture a depth of detail that isnt always easy to achieve in watercolour.

I prefer oil over watercolor because oil paints give artists longer time to work on details. Color blending is also easy in oil paint. It would be a nightmare to blend colors in watercolor pefectly on a big canvas unless if I have that lightning speed. Watercolors are also easily erased with water while oil paintings last forever...