The majority of British Best with pattern welded barrels had 3 Iron.
https://docs.google.com/document/d/1YJxP1k3PzmtmrG1HEGxd8X6g0-1GL0KNY8WMIMkdKr0/edit

Higher grade U.S. doubles were more likely to have 4 or 6 iron crolle, or Bernard I or II

There was essentially no difference 2-3-4-or 6 in strength so the choice was primarily aesthetic & cost, directly related to the complexity of fabricating the tubes.