I’m a newbie, only been on two Africa hunts, so not the experts many are that have commented above. After reading most of them and from my experiences, I’ve distilled it down to three key reasons to take your own rifle -
1) An African hunting trip is the adventure of a lifetime, taking a Cape Buffalo only makes it more so, and for me the process of deciding the rifle/caliber(s) to take, finding accurate loads, practicing etc makes the adventure last longer and almost doubles the fun. Squeezing the trigger on your hunt takes a fraction of a second, the entire process is what makes it a memory of a lifetime you’ll never forget.
2) They’re called DG for a reason, I can’t imagine putting myself into a risky situation without practicing adequately with the weapon and having 100% confidence on the things that you can control.
3) Extra costs and hassle traveling with the firearm - both of which to me aren’t that much - are easily worth it due to 1 and 2 above. As has been said if it truly is one hunt you can sell the gun here after the hunt and be out very little, or who knows find a deal and have a proven tack driving big bore that’s set up you may even make a little. I’m checking bags anyway and the process is not that hard and I’ve had no issues on my trips traveling with firearms.
Edit to add, on this, my most recent hunt was with 3 first timers whose first thought was to rent. After talking it over, detailing the process, and making similar points to them that I did above, they all 3 took their own rifles and are glad they did! And this was just a PG hunt.