With the release of the Mutant Mania minifigures, by Moose Toys, I figured it was a good time to explain some common qualities some collectors favor over than others. Keep in mind, no one collector feels the same, but these are certainly my guidelines and I think I may be in a majority. I don't think it's anything about taste, but being able to keep a collection uniformed.
Size. Most keshi are an inch and a half to two. They certainly can get a little larger, and if they do, it's no a deal-breaker, but some collectors like me will only follow toy lines with smaller and more familiar scaled minifigures to classic lines.
Articulation. Much like paint opinions, classic lines had no articulation. They were "slugs" or single mold castings, and how they are released from the mold is how they are. They are figures that are in one solid chunk.
Of course there are exceptions, and every collector is different. Moose Toys creates some cool lines. For example, I collect their Trash Pack minifigures despite them being a little small and painted, but I think I am going to pass on Mutant Mania, which is unfortunate. They are clearly inspired by old cool lines like Kinnikuman, but they are too different for me to dive in. If they were single mold, I think I would have. To be honest, the stretchy spine component was the deal-breaker for me, but I'll certainly look forward to see what they release next.