Most guys on these type of pages definitely go for the knobbies. Seems they last around 1K-3K miles. With my 90% or more rice rocket experience on motorcycles, I prefer the big block tread pattern (Continental TKC70, Shinko 705, .....) I have used since the 1970s.
Obviously the big block tread pattern isn't going to give as good of traction on mud, wet grass, ..... than knobbies. But, getting 6K+ miles on mostly pavement and isolated instances of near trials type riding while performing flawlessly is a huge incentive for many. The traction on pavement is almost unbelievable, I don't hold back, but I'm not a pavement racer either.
Steel belted radials tend to be relatively widely available for the big block tires too.