Sequential GUID or bigint for 'huge' database table PK
I'm in a similar same situation. Currently, I'm using the sequential GUID approach and have no fragmentation and easy key generation.

I have noticed two disadavantages that caused me to start migrating to bigint:


Space usage. 8 bytes more per index. Multiply that by 10 indexes or so and you get a huge waste of space.
Columnstore indexes do not support GUIDs.


(2) Was the killer for me.

I will now generate my keys like this:

yyMMddHH1234567890


I'll be using a leading date plus hour and having a sequential part after that. That allows me to range-query my data by date without any addition index at all. This is a nice bonus for me.

I'll generate the sequential part of the bigint using a HiLo algorithm that lends itself well to being distributed.

Hope some of this transfers to your situation. I definitely recommend using bigint.