So far, I've decided my habit of Diet Pepsi is likely less harmful (and less expensive) than tobacco or alcohol - neither of which do I use. I resent the price increases, but have decided (for now) that my "bad habits" are not that bad or expensive.
I agree that DP is sweeter than DC and maybe that's why I like DP - though I do love Coca Cola - but never drink it because of the sugar.
In a pinch, I can make do with Diet Coke. At the fountain, I'll mix DC with Coke Zero sometimes - if there is no DP available. I hate addiction in myself but figure DP is a lot less destructive than some other vices I've either given up or never tried. YMMV