It sounds like a daft question, but I was wondering if you feel like you play better with models you have taken the time to paint? Or do you tend to "look after" and play more thoughtfully the models you have put a lot of time in to painting during a game?

I'm not great at painting miniatures, but because I started airbrushing model planes when I was 6 or 7 back in the 80's I'm now awesome at vehicles as some of the younger players at my club tell me. I also sell a few of my pieces regularly so I guess I must be okay. For stuff I intend to keep I often spend weeks masking, airbrushing, stenciling, highlighting etc until I get it just right and as a result I feel I play those units more carefully and thoughtfully. I've never fielded a purely undercoated vehicle/suit/mini so can't really compare, but there are a few players in my club who field what I can only describe half mangled pieces of GW plastic that look like they used a paintball gun to paint, or in some cases have been unbelievably badly undercoated with a black or white spray can. More often than not these players lose quite badly compared to similar armies that have been painted. It's not about the quality or skill of the painting, but that the player has put time on their models