HDCD and XRCD. Which's one sound better?

XRCD is not a format. It's a mastering process, or at least the brand name of a mastering process. HDCD is kind of a hybrid, but it does require a decoding chip to gain its full benefits. And its claims to technical superiority (as opposed to just good mastering) are open to challenge.

As "formats," neither will sound better than the other. If there are recordings available in both forms (I don't know of any, but there might be), either might sound better. I'd put my own money on XRCD, however, because JVC does really good mastering.

XRCDs are by far better, especially if your player does not do HDCD.

Worldcup,
As far as the sound quality goes I whole heartedly think the JVC XRCDs sound better. I don't know of any recordings that are covered by both. With or without the HDCD decoder, HDCDjust doesn't sound as good to me. Most likely it is the mastering by JVC. All of the XRCD artisit are from the JVC library which does limit the artists that are available from them. I do like that I hear a remarkably good sound from XRCD without a special decoder chip.