Interestingly I had the exact scenario of 1 sailor out on the wire and another on the tramp in last wed's evening sailing, identical boats in about 10 knots of wind, the only real difference was one fattie and one whippet.

The fattie out on the wire was marginally slower to the mark ( but much faster over the water ) than the whippet flying a hull going downwind to the mark. Talking later in the bar to the better sailors in the group, all seemed to feel that its better to get the hull flying and turn downwind as much as possible, the only time to be out on the wire is if you are likely to over step the mark.