We have a similar situation at my place (Fabrication, steel erecting) and funnily enough we have both the characters you describe. But we're getting rid of both of them, hard times in the fabrication world at the moment. It is a tough choice, and in these times the best thing to do is to get rid of the one who is doing below average work but tries hard. At the end of the day, the aerosol is getting the work done and at a good standard, in turn making money.