Conversion with 4.2 much sharper than with 5.3 --??

I developed that image today in 4.2 in WinXP and as expected it looked nothing like the provided TIFF.

There’s not much point trying 4.2 - it’s old, long unsupported, and I can vouch that things improve from version to version, so you really should be using 5.4 (soon 5.5).