I own both. I've never thought of them as similar, they play totally different. I have 9 or 10 games set up at a time, these 2 have been getting the most play lately. I personally think DI is the better game of the 2, and probably has more staying power. I've also seen some fantastic deals on DI lately, it's a lot of game for your money.
You are probably waiting a long time for the Pirates rerun or a GnR. Grab a DI and when the next pin is available 6 months from now sell either Wonka or DI to fund it.