Regarding resolution and sharpness, it's a huge improvement compared to the other scan. A few minutes of alteration on the new scan blows away the other one as you can clearly see below. Still, It's going to need major repair and cleaning. Your scanner isn't doing this artwork any justice. The different scans are not matching up well in color, brightness etc. It's great for someone like me who would take the time to match it all, repair and clean it for low res MAME artwork.
If I were you I would take it to a good print shop and get it scanned in one pass on a pro machine at 600dpi. Then have someone you know with a good work portfolio restore/repair that scan. Your present scans aren't ideal, however they can definitely be used to make a print.
Thanks for sharing that scan Paul. It's really appreciated. Do I have your permission to make some MAME artwork from that and post it for the public?