There are definitely pros and cons either way. I have toured alone and with others. Depending on the group dynamics you may actually meet more people and see the country better if alone.

I definitely didn't find being alone to be a problem. You can get rolling as early or late as you like, ride as long or short miles as you want, stop where you want, and eat what you want. On routes like the Trans America or the Pacific coast you meet enough other riders that it hardly seems like being alone. Even when I don't meet any other riders I typically find plenty of interesting local folks to chat with.

Personally I wouldn't try to seek out someone to tour with and would just tour alone unless there was someone whose company I really enjoyed who was interested in going with me.