+P loads are simply a way to get more performance out of a given chambering. If the firearm can handle the additional pressure, and the load is accurate enough, then why not? My daily carry load for .357 Mag in South Africa was a +P load for a very lightweight projectile
(NGA Eliminator). It dealt out rifle-like shock on anything soft, because of the high velocity. It was spectacular to see what it did to milk bottles full of water. Now it isn't everyone's cup of tea, so each to their own. There are people that will ditch a rifle in favour of a "better" calibre, so why not stretch the operational envelope of your existing firearm?