a) Samples. MAME's -listxml output lists samples without any hash or size information. That's the basic reason why there is an external datfile which does list these info. MAME's -listxml output lists several clones as 'sampleof invaders' while invaders itself doesn't use any samples anymore. So this entry is wrong and cmpro (before 3.106a) fixed this by removing the sampleof relationship. THat's why you need several invaders sampleset clonesets. This behaviour has changed since 3.106a and now you only need the invaders sampleset.
To sum it up: If you use cmpro 3.106c and the latest sample datfile you won't see any difference (dat vs exe) when scanning.

b) Again, there is no need to use a not up2date MAME version. If you need old datfiles you have to search them yourself. I personally never understand people to collect rollback files. There is no use to collect wrong sized and bad dumps. The datfile names are chosen by the author what suits best.

So it's rather easy to answer what to use: The latest official MAME and the latest artwork (flyers/samples/etc) dats for that version.


Roman Scherzer