What represents a good entrepreneur? Some would think a talented engineer furiously coding on a clever algorithm; or the CEO in his suit winning some award. I think those are only a tiny fraction of startup life. They are not as interesting as one might think. If you are an experienced programmer and you know what needs to be done, you just go ahead and code the solution out. It's like a good walk in a park. Enjoyable but nothing fancy. Winning awards? It's an important milestone but not a good indication of the process.
I think it's the ability to make good decisions. By definition, a good entrepreneur is the one who makes most important decisions right. A corollary is that for a startup with two founders, it's about make the right decisions together.
The two founders should come out of the debate with a better idea, one that weren't there in their mind before the debate started. This would require the two founders to sit down, carefully listen to what the other is saying, comb through what works and what not, acknowledge the weakness of his own solution and, usually as a by-product of doing all the above, creatively come up a brand new idea that takes the best parts from both while avoiding the known problems. If you can do that, you've got a winning team.
PS. When people say a solo founder is really hard, they probably mean solo founder doesn't have someone to bounce off ideas with. Hence he may miss the opportunity to get to a better solution. So in my opinion, if you are a solo founder, go find yourself a strong advisory board, have someone you trust and use them to tease out the best ideas that weren't in your mind.