Any preference between the two? They both look like they will match my live rock fairly well.
If you call the guys at marco rocks you can tell the kind of pieces that you are looking for and they will do their best to help you out. I also think they are little cheaper.
I like marco also.. Plain reason is like Hannah said if you call Marc and tell him what sizes you want from rubble to football size he will do everything he can to help you out. Makes aquascaping easier..
Don't know about the eco rox, but I was recently at an LFS that had marcorocks. The guy there told me the pukani I ordered from BRS would look the same as the marcorocks, but when I got the pukani it was 100x better! From what I've heard, eco rox are very similar to pukani, just a little more dense. You could always split the difference and order some of both
I went with Marco and didn't call or anything and still ended up with exactly what I needed. Actually ended up with plenty left over too...