Starting companies is much easier with a cofounder. There's more momentum and pace with somebody together. Especially with first time founders, a team is the driving force when starting a venture.

But unfortunetaly every relationship changes or ends at some point--always. Then, it's about a quick and smooth separation without briging the company in danger. But this rarely happens, the separation is usually a tedious process over many months till the company breaks.

So yes, solo founding is better in the long run but in most cases there will be no founding at all because of momentum lacking.