I'm not sure where you're getting the numbers for your conclusion that the 330U had more drawbar HP. The Nebraska Tractor Test numbers are:
* * * **PTO HP** **Drawbar HP**
model (max) (rated) (max) (rated)
300U: 41.26, 36.41, 37.36, 29.61
330U: 34.24, 29.95, 31.77, 24.31
The 330U compression ratio is higher (7.38 vs 6.8) so it may be a bit more efficient, but the 300U still has the edge in power.
Afraid I'm not good enough to tell you what's in the picture, but certainly could be a 300U - chances are good it is since about ten times as many of them were built as 330Us. Hope you enjoy whichever it is.