Never thought about it really, as I have always had a (female) nurse. If I had a choice of male or female, I would pick female.
When I make an appointment, it says on the little appointment card '2pm appointment with Mandy or Liz or whoever,' and I KNOW all the nurses at my medical practice are female. If I went in and it was a man, and I was uncomfortable with it, I would refuse to have it done.
I went for a smear once (about 10 years ago,) and the nurse - who had only just started 2 months back - was the mother of one of my daughter's classmates. 
No.
Fucking.
Way.
I don't care how professional or discreet she was, no WAY was she seeing my fanjo. I would never have been able to look her in the eye again. I actually thought it was wrong having a nurse at the local medical practice, that was one of the mothers at the local primary school. Just too familiar. And no way was she giving me a smear.
I went in and cringed when I saw her. She said 'errm when did your last period finish?' I knew it was 10 days ago, but I said 'yesterday,' (knowing the smear could not be done then!) So she said 'oooh, sorry you will have to wait til next week.' I think she was as relieved as me.
So that is the only one time I have not let a female nurse do it.