Some folks media blast first, then see how bad the panels look. One car on this forum, the roof looked like swiss cheese when the blasting was done, obviously needed a new roof skin.
Patching panels is time consuming and requires perfection so you don't warp the panel due to the heat of welding. So is the time spent there less expensive for you than buying a new skin?? I'm not the best welder of thin gage sheet metal, and the paint shop warned me that cutting and patching panels can eat up a lot of hours shop labor (fitting, welding, smoothing weld seam, bondo, etc) They recommended replacing complete panels, which is the direction I'm going. I hate to spend $$$ on a good paint job and have rust start poking thru later on.
JMHO.