I am trying to isolate primary neurons for cell culture and am wondering if there is a difference between using Penn/Strep vs. Gentamicin for my neuronal media?
Penn/Strep is the most commonly used. Also you will find Penn/Strep/Amphotericin B mixes which cover a bit wider expectre. Watch out for gentamicin use, it may result a bit toxic for primary cultures.
Antibiotics aren't 100% necessary in culture media, I rarely use antibiotics to protect my primary cultures, in general a careful handling is enough to keep contamination out.
I agree with the previous answer. gentamicin seems to exert some sort of toxic effects of primary cultures. Penn-Strep is the most commonly used one. Again, the decision to use antibiotics in culture media depends on your special situation in the lab. If you are sure of not getting contaminated by other fellow users of your incubator, you don't need them. But if you end up using it, go for Pen-Strep.
Gentamycin is toxic so is likely to cause other issues. use pen/strep. on our primary epithelial cultures we also use kanamycin and metronidazole with pen/strep