I like the first photo. The J15b's were quite nice looking locos, though not with the best reputation. Still an improvement over the J15As with their extremely conservative design. Neither class could beat the original J15, it seemed.
I seem to recall someone, perhaps Milne calling for locomotives similar to the cattle engines to be built as a standard locomotive, presumably to replace the J15s. Perhaps their high maintenance (a feature of the wider MGWR fleet, apparently) put Inchicore off replicating the design.
I think it was Nock who er...knocked the MGWR in comparison to the BCDR, noting that while the BCDR used its steam locomotives efficiently, it was not unusual to see dozens of locomotives sitting around Broadstone in the middle of the day!