to me is the perfect Rolex if I could only have one. It has great size at 36mm, clear and legible dial with iconic 3-6-9 indexes, you can either dress it up or down.
But if your heart says it's the 1500, then you should follow it. Most importantly is that you have a try on the wrist before deciding to do the purchase, and the 1500 comes in a lot of dial variation. It is quite versatile too , not having the legibility like the explorer is a downside but it is still more legible than most other watches in the market.
As for the diameter, the 1500 measures 34mm and 1501 measures 35mm due to the difference in the bezel.
Hope it helps. And I wish you all the best in your search for your first Rolex!
Sam