It also depends on what you regularly guide for while hunting.
For elephant in real thick stuff a double makes sense and is hard to beat. However a big enough bolt gun you can handle well is just as good.
When following up on wounded leopard a double makes sense as you do not have time to cycle the bolt if your first shot does not stop the leopard.
Doubles are very expensive. Doubles are temperamental with what you feed them. The regulation determines the load and often the bullet you can use. Competent reloading takes a lot of practice and commitment.
Big bolt guns can be loaded with any bullets and easily sighted to match the load.
I could never afford a double when I started hunting and my mentor used a 500 Jeff. I at the time had a 375 H&H that I used and must admit that it seemed awfully small compared to the big 500. After seeing the devastating effectiveness of he 500 Jeff, I acquired one on a ZKK 602 action. It was a decision I have never regretted and it has been used on many DG with the same devastating results many times. I still own and use the 375 H&H though.
After a close encounter with a wounded leopard, I felt the need again for a medium double rifle, I would have prefered one in 9.3x74R, 375 H&H Mag flanged or 450-400(a big heavy double is not so suited for this work), however I still could not afford one. I decided to settle for a poor man's double. I bought a sxs brno sidelock shotgun, had the barrels shortened to 24 inches, fitted a front sight and a rear ghost ring. Using Brenneke slugs I shot many plains game while testing it and this ended up being my leopard backup double. Light in weight, very easy to swing and aim, even if the first shot did not stop the cat you could feed it your left arm and give it the second barrel using only the right hand and arm.(Luckily I never had to do this). Very effective and I still use it to this day.
When hunting DG and travelling I just grab the big 500 Jeff and the poor man's double and I am ready for any eventuality.
I still yearn for a big double with 2 sets of barrels but the 500 Jeff bolt gun has works so well and has been so devastatingly effective on everything that I have had to use it on that I could not justify leaving it behind in favour of a double.
In the end for a PH it boils down to what he is competent with and what he has confidence in. If a particular rifle or cartridge combination let's you down you will not trust it again.
If however, like my 500 Jeff has done on many occasions, the rifle cartridge combination gets the job done effectively, you will come to trust it and your confidence in the weapon will be such that you will trust it and it's ability with your own and your clients life, because it works, each and every time.
