If you can, you must. Ive done two proper African safari's, the last one in 2005 to Kenya/Tanzania for 10 days, it was amazing, saw/photographed the Big 5 plus many others, but I was still shooting film then, on Pentax MZ-5 with kit 70-210 and a shorter zoom. I got many good photos thanks to our guide getting us real close to the animals (Lions within 10ft, Cheetah within 10ft, Buffalo charging our truck etc.). So I'd say the quality of the guide is a major factor.
The other time was in 2001 in Namibia, in Etosha self-driving mostly, which was also brilliant but I definitely could have used a local guide.