Last time I was at AF it was VMC in the zone. As an IFR flight we got a code from BN radar for a VFR departure with IFR pickup.Got under way with no delays. We were told to stay outside CTA. Departing to the south under the steps. Once outside the zone we called radar and resumed IFR but still had to remain OCTA.
Haven't been to YSBK for a while but departure to the west climbing in CTA resulted in a short delay on the ground due preceeding IFR traffic. It was VMC in the zone and there wasn't much traffic.
My limited experience a request for a VFR departure is quicker and you elect when you want to resume IFR. Keeps the departure much simpler. If you're climbing into C airspace immediately after departure I'm not sure VFR would help much because you still need a clearance. It works well going into G airspace though.