If the question is to AI or not to AI, I say yes, you should - but with disclaimers.
But, prior to that, I would ask what about a 243AI is inadequate for deer? I have a 243AI and love it, very accurate, easy reloading, and the extra few grains of powder gets me a few hundred extra FPS.
I had a 25-06 many years ago, sold it, and regret letting it go to this very day. It was a great rifle.
If going to AI, be aware that many will complain of the fire forming process, it wastes barrel life. Truth be told, I like my rifle as much firing factory 243 as I do firing custom loads, it is very accurate with both, and I cook pretty hot 243s to do the fire forming - and the gun doesn't seem to mind.
If the extra velocity isn't worth the effort, stick with factory SAAMI stuff and forget the AI route. If you want the option to go fast or go really fast, AI is a great option.
Between 243 and 25-06, I'm not sure which I would take. Both have killed lots of animals. Given that the 243 is a SA and the 25-06 is a LA, I'd probably do the 243, if only for the little benefits SA has over non-magnum LA.