I'm going to say PRTC Omnilink for the worst. Their 2005 Gillig advantages are quite frankly pieces of junk. The best in my opinion is probably WMATA Metrobus as well as DASH. WMATA takes good care of their Orion VII OG CNGs and New Flyer C40LFRs as well as their New Flyer hybrids. Dash takes care of their diesel Orion Vs pretty well as well as their Gillig hybrids.