Hello yidava25,
Your question is valid and definitely worth asking your PH (such a question will impress your PH because, he or she will then figure that you are a bright soul who, has desire to learn things about present day African Hunting Culture).
As for my opinion - being often unwilling or perhaps mentally unable, to keep my big mouth shut when things are going along just fine, the following is my two pennies worth:
Having been a former .270 Winchester fan and with it I've taken game in N. America, including Alaska and Hawaii, not to mention watching a hunting partner take a few Namibian species with his .270 / 140 gr A-Frame bullets, I agree with those who say essentially; "Put a sturdy bullet in just the right spot and your critter will tip over very soon thereafter." (shoot straight and avoid cheap/overly soft bullets in high velocity cartridges).
You do not need to run out and buy a dreaded .300 magnum for plains game hunting in Africa.
All that being said, after adding an African hunting safari into your list of life's experiences, you may or may not conclude that some other caliber is in order for inevitable return trips to Africa.
If so, I personally do not share the general N. American opinion that a .300 Winchester is the best "multi-purpose" cartridge, as it pertains to most southern African hunting conditions - beware of "Velocity Madness", same goes for today's "Gigantic Scope Mania" (Overly huge rifle scopes are definitely not user friendly in typical thick bush conditions).
For my rifle buying dollars, I would only consider a .300 magnum if I planned to do some very long range shooting of thin skinned game (so called "Plains Game" or "PG" as it were, or possibly Western USA/Canada long range elk hunting, etc.), and for this, I have used one in Namibia (.300 H&H - of course the best .300 Magnum of them all - LOL).
But again my friend used his .270 Winchester and did just about as well as I did on Namibian critters, including larger ones like kudu and gemsbok (one zebra proved a bit tougher for his 140 gr bullets than another zebra did against my 180 grain .30 bullets, but not by much).
If you plan to hunt The Eastern Cape of South Africa or most of Namibia, your .270 might turn out to be just the ticket as those areas are generally wide open geographically speaking - longer shots there are common.
Most of the common hunting areas in southern Africa are moderately to thickly festooned with thorn forest and brush, a "long shot" in many areas is 150 yards/meters, across a water hole or narrow canyon, etc., most shots probably average only about 75 and not rare to shoot something at 10 or 20 paces.
For those types of hunting conditions, I would rather recommend cartridges such as:
.30-06 / 220 grain
.338-06 / 250 gr.
.35 Whelen / 250 gr.
9.3x62 / 286 gr.
Rant almost over.
As long as your PH endorses your .270 plans, (I expect they will endorse it) do bring it but like any rifle or archery tackle - practice, practice, practice and then practice some more.
Best regards,
Velo Dog.