When I started looking into enneagram(and still misidentified as a 5, in the meantime i figured out I am a 9) my interest was pretty much confined to my own types and those of a few friends of mine(4s and 8s mainly)
But after diving much deeper into the roots of the Enneagram it has given me a far better and more fundamental appreciation of every single type.
Ones are quite deep. I find them to be the least pretentious of all types because of their convictions. They never control out of blood-thirst or for their own self-interest. It truly is about right and wrong (even if that vision is sometimes skewed). And I think being so aware of the many times they fall short makes them merciful to others. The ones I've met in my life have always given the best advice. They're very empathetic, not so much in a "I've been there" way, but more in a "we're all just silly flawed humans, don't fret" kind of way. It's very disarming and comforting.
Edit: I thought for a sec, this thread was for ones only. I DO very much love eights and nines as well. I'm less familiar with them in my personal life, so any claims and conclusions would be from a book (unless you want to hear about my mom )