Hi 1tothe2,
That would always depend on your situation, the business type etc.
There are normally only 3 reasons for taking apartner in my opinion.
1. For financial reasons, split the start up / buy costs etc.
2. If you do not have the skills required for the business for e.g it is a car mechanical workshop and you are not a mechanic but your partner is.
3. Because you want to. Some people start business's with friends family etc just to share the workload.
In my thinking, i would never take a partner unless I had to.
you lose some of the creative and administrative control.
You share the profits...

You are not the sole decision maker.
And finally you will never ever have a falling out with yourself, but a partner....?
These are just my thoughts.