Oncologists know their cancers, but gynecologists are going to be familiar with cervical cancer regardless. I would say go with your gynecologist, just because you're probably more comfortable around him/her.
Your gynecologist is perfectly capable of taking a cervical biopsy for examination. It is a common procedure (called a PAP test) that your gynecologist no doubt does dozens of times each week. An oncologist treats patients who are determined to have cancer.