Obviously I'm extremely late to this post, but fyi:
The M42 is really a lot closer to the S50 in terms of bore, stroke, pistons, etc. In terms of general engine dynamics, you can think of it as a shortened S50.
The S14 is really closer to the M10...
which partially explains why, when BMW prepped their 2.0 litre engines for GT-2/3 they used the M42 as the platform, thus giving us the S42