I've lived both of these lives exactly. I had a partner for 8 years with no friends. Now I have no partner but tons of friends.
My verdict: friends. This life is literally 10x better than just being with my girlfriend but living alone. At first it was fine, I could hide from the world and I had a love and my life was actually quite content. But eventually I started to get antsy about being shut off from the world, and it certainly lacked a lot of fun that everyone needs in life. When there's just the one person, everything banks on her, and if she's mad, your life is miserable.
Right now I have all friends but I'm getting antsy over not having partner... however, the fact that my life is so fulfilled by so many people and everything is just in place so wonderfully, I'm having so much fun and having lots of great relationships with people that I could stand to live like this for a far longer period if I had to.
In order to get these friends I had to fundamentally change my outlook on life and everything about how I act in public. I love that I've changed, not at my core of who I am, but with my confidence and social skills to be able to attract lots of friends to myself. That kind of life is so much better to live.