For me at least, it varies. One of my fondest memories (and possibly one of my best life memories) is travelling around the US for three months with my best friend. I will likely never replicate that experience.
But that said, I just took a four day trip to Germany by myself and I loved it. I think I spoke less than thirty words to anyone on most of those days, and found it tremendously relaxing to just walk around a museum by myself, alone in my thoughts. I took a three hour train ride to Poland just because I wanted to, and I loved sitting there by myself watching people in rural East Germany go about their business. It's a lot more difficult to be a fly on the wall when you're with someone, because the minute you open your mouth it's evident you are an outsider.
But on the other hand, I'm extremely reluctant to approach complete strangers and strike up conversation. When I'm with someone, it happens naturally. When I'm by myself, I will be alone for the duration of my trip.
But that said, I just took a four day trip to Germany by myself and I loved it. I think I spoke less than thirty words to anyone on most of those days, and found it tremendously relaxing to just walk around a museum by myself, alone in my thoughts. I took a three hour train ride to Poland just because I wanted to, and I loved sitting there by myself watching people in rural East Germany go about their business. It's a lot more difficult to be a fly on the wall when you're with someone, because the minute you open your mouth it's evident you are an outsider.
But on the other hand, I'm extremely reluctant to approach complete strangers and strike up conversation. When I'm with someone, it happens naturally. When I'm by myself, I will be alone for the duration of my trip.