Consider a couple of things in arriving at an answer to this question:
a - what do you use a compressor for in recording a vocal.
b - what are the key principles to getting good sound to tape / disk.
For a - the key is to get a vocal recorded at a good level, so it will sit nicely in a mix, without having to worry about the vocal's dynamics. Equally important, without having to put to many restrictions on a vocalist's performance.
For b - something which seems to have become more-and-more a forgotten principle in recording ...... yet it is THE KEY principle in getting a good sounding recording: Get the recording to tape / disc in the way you want it to sound in the final product!! In other words, minimise processing after the recording as much as possible. In other words, avoid "double" processing. In other words, the less processing, the better the final product will sound (if you track it right)
I Could add at least 20 other reasons why to process GOING to tape / disk and not after. So, put your processor(s) in the chain to your recording medium. Spend time getting it right from the source.