What sort and sizes of tooling are folks using? Upper/lower limit?

Recently I’ve been looking for larger V endmills.

I recently picked up an Amana RC-1142:

but wasn’t willing to use it due to the vibration (insert seemed fine, and tool seemed balanced), so am going down size-wise to an RC-45711:

Though I’m wondering if I shouldn’t have tried the 45751 instead:

All of this though, really makes me wonder why such tooling has 1/4" shanks and wishing that some vendor would make such tools w/ 8mm (5/16") shanks — anyone know of such an option?