I can't really say if you'd be better off, it depends on what you want additional lights for. Roof lights and ditch lights serve different purposes, so it might be better or might not.
To clarify, there are some valid reasons people might run roof mounted lights, but I've tried it a few different ways and I never could get them to work to my liking. There's the back reflection problem george alluded to, in rain, fog, or dust all the light reflects right back to your eye so it's almost like driving through a haze. The main problem I had with them is it tends to flatten everything. Because the lights are mounted higher than your eye level, any shadows from the road are hidden from the drivers point of view. So instead of highlighting dips or rocks in the road, everything tends to look flat and smooth because you can't see the shadows being cast. Mounting lights at bumper level or lower exaggerate the shadows and make it a lot more noticeable for the driver.
I think roof mounted lights work best if used for long distance lighting when running at high speeds. Then you're just looking to illuminate things farther down the road and position doesn't matter as much.
I might also be in the minority in that I still prefer halogen lights. When I used to do a lot of night driving, it seemed like LED's and HID's always caused more eye strain over long periods of time, and halogen lights seemed to penetrate the darkness much better.
