An interesting comparison might be how many B101 kits were produced / sold. Not quite the same, of course, as it's a kit - but - a kit can sometimes sell more because it's cheaper, but less because it's not RTR! There were 16 x B101, they were shorter lived, and travelled much less widely.
A Mallow - Waterford based layout (long overdue!) would need 121 and B101 classes, as these were the mainstays in the 1960s. Probably the only line where 141 and A classes were LESS common than these classes.
A good selection of goods vans, particularly the H, would also be needed.
Passenger stock was generally laminates in the 60s, with a few old Bredins and the odd wooden bogie. While I'm sure PRs went there, though no recollection as such, has anyone ever seen a picture of a Craven in a train consist on that line? Cravens appeared in 1963, and the line closed in 1967.