Need help. Is 300 Blk worth it?

Figured i would ask this here. I am looking into getting another firearm mainly for home defense & to bring with me on hunting trips in a backpack. No i wont be hunting w/ this firearm but would have it with me just in case as i hunt about 2-2.5 hours away from where i live & would like to have something on me other than my handgun. But like i said it would mainly be for home defense. I have been thinking of getting the sig rattler & a can to go with it or the b&t SPC 9 SD which is a 9mm.

The only thing that is holding me back from the 300 blk is the price of ammo as i have other guns i like to shoot & don’t really have the money to spend on 300 blk to shoot it as often as i would want too. With my guns i like to shoot them instead of letting them sit so i feel like it would bother me if i had the rattler but didn’t get to shoot it often. As w/ the b&t in 9mm i will be able to shoot it more often due to the cost of ammo. But at the same time i know 300 blk compared to 9mm would be more ideal for home defense.

Those of you that have a 300 blk pdw style weapon are you happy you went that route & would you recommend it?