Gun size dictates holster type, they go hand in hand. An ankle holster for a Desert Eagle would be unpractical. I have been carrying for over 30 years I use different holsters for different guns for different purposes. I use a strong side belt holster when working and generally a shoulder holster when not. The shoulder holster is great if I am in the car all day and the belt holster works if I want more security and maybe on my feet all day. Mode of dress dictates as well.
My rifle and pistol are tools, I am the weapon.