And I don't know which choice I should pick.
The good old fashioned attack speed has been working fine for me, but then we got the shadow-defense changing me to damage up, or this other armor doing other things, it's just too hard to pick a choice out of all of these.
My gun collection is rather... Minimal. Im planning on getting Phantamos and a Callahan/Iron Slug?
Though sometimes I just swing my sword around cause it's a bit easier.
I have a detailed armor guide that you might find useful.
Are you talking about 4-star Gunslinger armor, meaning Sunset Stetson and Sunset Duster? My guide advises you to choose Shadowsun, because the blanket gun damage+2 cannot be replicated through unique variants. I mean, you can get ASI and CTR through unique variants (and heat and Swiftstrike Buckler) but you cannot get a damage bonus against all enemies. Another nice feature of this plan is that you can seamlessly switch to Chaos or Black Kat someday, if you want to.
Let me know if you find this helpful, or if you have further questions.