The comments section to Dilip's reply is overflowing.
First - the OP (Graphth) is correct in that credit scoring has become a game. A series of data points that predicts default probability, but of course, offers little chance to explain why you applied for 3 loans (all refinancing to save money on home or rentals) got new credit cards (to get better rewards) and have your average time with accounts drop like a rock (well, I canceled the old cards). The data doesn't dig that deep.
To discuss the "Spend More With Plastic?" phenomenon - I have no skin in the game, I don't sell credit card services. So if the answer is yes, you spend more with cards, I'll accept that. Here's my issue - The studies are all contrived. Give college students $10 cash and $10 gift cards and send them into the cafeteria. Cute, but it produces no meaningful data. I can tell you that when I give my 13yr old $20 cash, it gets spent very wisely. A $20 Starbucks card, and she's treating friends and family to lattes. No study needed, the result is immediate and obvious.
Any study worth looking at would first separate the population into two groups, those who pay in full each month and those who carry a balance. Then these two groups would need to be subdivided to study their behavior if they went all cash. Not a simply survey, and not cheap to get a study of the number of people you need for meaningful data. I've read quotes where The David claimed that card users spend 10% more than cash users. While I accept that Graphth's concern is valid, that he may spend more with cards than cash, there is no study (that I can find) which correlates to a percentage result as all studies appear to be contrived with small amounts to spend.
As far as playing the game goes - I can charge gas, my cable bill, and a few other things whose dollar amounts can't change regardless. (Unless you're convinced I'll gas up and go joy-riding)
Last - I'd love to see any link in the comments to a meaningful study. Quotes where conclusions are stated but no data or methodology don't add much to the discussion.
Edit - Do You Spend More with Cash or Credit? is an article by a fellow Personal Finance Blogger. His conclusion is subjective of course, but along the same path that I'm on with this analysis.