I am having a JP enterprises trigger installed on my Colt AR15 model A3. The default trigger weight is 3 1/2 pounds. However, JP tells me that at 3 1/2 pounds, the gun may not reliably shoot NATO or forgien rounds. I can ask them to leave the stock spring it. This will result in a 4 1/2 pound trigger pull.

I doubt I'll ever use NATO or forgien rounds. I use the gun for fun, varmits, and plan to do some tactial competitions with it. So, I was going to go with the 3 1/2 pound pull.

This is my first AR15. Any advice would be welcomed. What do you think? Should I go with the 3 1/2 or 4 1/2 pound pull?

Go for the 3 1/2 pound pull.  In the unlikely event you have problems later, a new stock sping will run you a couple bucks.