I would take the latter option (Grandmother + Prologue) on the assumption of a greater breadth of sounds. That said, I am not particularly one for organ-style keyboards (modular guy here). For my partner however (a pianist) I might go Matriarch.
Here’s a recent album for reference (we’re possibly a bit unusual in our approach, and the first track might be particularly so):
Here’s an article that breaks this down a bit between the Moogs:
I’m sure you’ll make the best choice for you. Perhaps picking up a used Prologue from a reputable source would be a deciding factor. If you aren’t into it, you could likely move it along with very minimal loss.