Are you talking about what they now try to pass off at the cold cut counter and "corned beef"? IMO that ain't no corned beef. Corned beef and or pastrami can only be from one thing IMO.............................brisket
Larry, I agree. The last butcher around me that pickled his own corned beef has retired. I could go in and pick the piece of brisket I wanted and tell him how many days I wanted it in the pickle. It was Great. I sure miss that corned beef.
Since corning is a process that can be applied to different cuts, I'd say it depends on personal preference. If you like the grain and structure of a round, give it a try. I recently had corned beef made from the shoulder (by Miesfeld's of Sheboygan) and it was very good.
I've had corned beef made with a Eye of Round and Knuckle before and I liked them.
Never tried the waygu rounds but I did find this.
I goofed up one time and used a BNLS Rib eye and it came out excellent! https://tvwbb.com/threads/yes-you-can-eat-your-mistakes.78567/