I've done both. It is better to go single than have a founder who isn't in sync. If you can find a founder who is in sync with you, that is best. But most of

I've done both. It is better to go single than have a founder who isn't in sync. If you can find a founder who is in sync with you, that is best. But most of the startups I've seen fail, even though the blame was placed elsewhere, really boiled down to conflict between founders. No market fit? Because the founders couldn't agree to listen to the market. Etc. Etc.