It all depends on my mood at the time....

It is nice to be one your own once in a while, for some quiet time. But I also noticed that most horses will be more jumpy, and harder to handle when alone.

With friends it is fun, I have even gone lots with groups of around 7 people (the place where I board has a lot of nice people in it ) and groups make almost any horse easier to handle (in my case at least) though then again they dont learn how to do it on their own.

Basically all personal preference