You have to make that decision, no one here can make it for you. There's no doubt that a semiauto with an empty chamber is safer as far as accidental discharges, the worst of which is a small child finding the gun and pulling the trigger. But you're at a huge disadvantage if you have to rack the slide and fire quickly.
I don't know why your friend has the idea that a chambered round is more likely to jam a gun. Ignore that reason.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek