Alek, Dark AleX's webmaster, has come upon some information about Datel's Action Replay for the PSP that you might want to know. Suffice it to say that you're really better off with CWCheat.

According to Alek, Action Replay uses code from other developers, interferes with Custom Firmware code, and compared to CWCheat, takes up a lot more memory and has a pretty small database:

• Datel' Action Replay does uses code that isn't from itself, code that isn't distributed to be used the way they use it anyway. The code involving this terms is, for first instance, the Pandora forged IPL block, and on second place but of course not less important, Booster's IPL SDK.
• It has been confirmed that Datel' Action replay does interfere on the Custom Firmware code
• They use a bigger memory footprint due to the graphics involved in it, and it's interesting also to mention that they had a pretty small database, that being compared it to cwcheat one, this first one isn't even a database tbh.

Dark AleX himself confirmed these. Looks like the guys who chose to stick with CWCheat were right on the money. On precisely US$ 39.99 worth of money, which is what Action Replay is going for. It seemed pricey before, but now it feels like you're just paying for packaging.

Thanks to CJ for sending in the tip!