Board Thread:News and Announcements/@comment-26581304-20150906194347/@comment-26927141-20150913180457

Cobalt-Mammott:

In short, if you believe the Rare calculation happens first, it's better to breed Potbelly and T-Rox because failed attempts will cost less time on average since some will be either Potbelly or T-Rox rather then the more costly Enbrat. If you believe the Type calculation happens first, then it's better to breed Rare Enbrat and regular Enbrat since that combo has a 100% chance to trigger a chance at a Rare Enbrat.

But lets say it does calculate for a rare entbrat and it comes up negative. So that leaves the chance for the other results of that breeding combo: trox, potbelly, or non-rare entbrat. Either way you choose, you may breed non-rare entbrats, which will still be time consuming.