GRP, please. They are all coins, putting a C in the three-letter code is redundant. GRP obviously at a glance means GRouP, so it is much better code to use.

Because of the limited time-window to pick up I0C, GRP, CLC and XGG by merged mining, I think block eruptor USBs were worth buying, as lookie now, already I0C and GRP have been picked up by bitparking so are now high difficulty; it was worth grabbing them before that happened. Same likely continues to apply to CLC and XGG.

-MarkM-