Vanilla Extract Vodka Quality
I have family in Reunion Island - one top seller of bourbon vanilla. The only vodka they have there is imported, and rhum (or rum if you prefer to spell it that way) is readily available.

Personally I would recommend:


150 ml / 5 oz. of neutral alcohol (e.g. rhum, vodka, eau-de-vie)
2 beans
8 weeks (6 min) without light, occasional shake


You can also use syrup instead of alcohol, but concentration / flavor will be different.


5 oz agave or sugar cane syrup
2 beans


AFAIK:


vodka is not mandatory
use any vodka you like (e.g. could be in your cupboard already)