personally I would buy originals where possible...
they generally have better ergonomics and I prefer to give my money to original designers - after all they did most of the work - plus Emilie has been fantastic with support when I've needed it - and I think that they'll probably hold their value a bit better and be a bit easier to sell in the future, if the need ever arises
I generally think eurorack modules are small enough without shrinking them further and using trimmers instead of proper pots/knobs - as they are more difficult to use/less precise - but then I've got my average cost of racks down to under £1/hp - by DIYing cases and power supplies - so I don't care that much about rack space (and I've got quite a bit left over) - might need an extra power supply at some point - but that's not much - and I might buy a second mantis - which will put the average price up a bit...
I've got quite a few mutable instruments modules, but saying that I've also DIYed a few and have some left in my backlog - but they are all full size or bigger in a couple of cases - and personally I'm not keen on small smd soldering - especially electrolytic capacitors! so I doubt I'll buy anymore once I've finished the ones I have
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities