Both are pretty good buys IMO, as long as you buy the correct property that suits you and your investment plans.
I was in Emerald from 02-08 but then went over to M'bah.
Good thing about buying in Emerald is that you're on hand to do repairs yourself when needed, because I'm sure you've witnessed how hard it is to get a tradesman to turn up in any set timeframe!!
We bought two properties in Dalby in 07 and 08, they've worked out well for us. I was looking at buying in Emerald for ages, but would have lost my highly subsidised accom if I did.
Looked at Roma for a while, not bad buys there either, and have just put in an offer on a place in Toowoomba.
Happy to help with any further questions, but a lot of ppl on here know plenty more than I do!