I don't mean to contradict the other opinions, but in my own experience, Friday slots tend to suck.
1. Your only on a 100w station, which means the IDEAL distance of air-play you're going to get is 100w, but depending on weather, equipment, etc., you may not even broacast at that level, so trying to hit some "mass Friday market" is sort of irrelevant.
2. You said you'll be playing electronic, essentially party music. That might be cool on a Friday 7-8 on Fridays, b/c people will be getting ready to go out, driving around, etc., and you'd make good background music. But that doesn't necessarily equate to a steady listenership, because on Friday people have other things to do in the evening.
3. On a 6-8 slot on Wednesdays, you'll be getting the tail end of the rush hour drive-time people who will be flipping around on their car radio stations. Those people could come to expect to hear you every Wednesday night, and religiously tune in. Also, high school kids are at home already, college kids always have time, so you'd be hitting just about every demographic that likes your music. Plus, it's Wednesday night. People don't normally make plans Wednesday night, so they are more willing to sit around and listen to the radio.
4. Coming from a more personal rationale, I would lean towards going for the Wednesday slot, because it's an hour more to play my music. I always found a one hour program as a waste of my time, by the time I got to the station, set up my rotation, played all the legal IDs, etc. It may be different for you, b'c I played rock music, so I dunno.
Just my $0.02.