Man, if a guide told me my 270, 280ai, or 30 06 was too small for his liking, I would likely not hunt with that outfit.
In your case since you have deer rifles, I'd buy a bigger gun just for the hell of it, doesn't mean you have to use it for elk haha. Thinking 300 win, 35 whelen, 338 win.
For someone who needs a rifle to mainly hunt deer and hopefully elk and does not have a rifle for this, I would have to suggest the 270 or 308 in a good fitting rifle that catches their eye.
Sometimes it's easier to hunt where you want and do what the guide wants with cartridge / bullet combinations. I've particularly found African PH's to be opinionated in this regard, including being unhappy when I showed up with 180 Partitions and not Barnes in one case and unhappy that I was shooting 168 TSXs and not 180 TSXs in another. Not sure what difference 12 grains of bullet would've made on that hunt, but I had to hear about it the whole time.
