If I remember correctly (it has been a few years since I flew the 700/900) it is pretty much within 100 or 200# We burn about 1600-1800 a side at .77, which is about where I remember it being on the 700/900 where I used to work (we did CI flying so our speed varied a lot there).
I do think the CRJ does a bit better on gas, but they are the same engines as on the 900 (crj-900 engines have a little higher thrust rating). I thought the ERJ would burn more to before I actually flew it, but it really isn't as large as I thought.
We were burning 2100 a side at FL360 a side today but doing .80 as it was the freedom leg.
The CRJ 700/900 burns about the same at .82 or more. Normal burn for 700 is 1800-1900 at .80 (obviously temperature is a factor). 900 is about 100-200 higher. Freedom legs on 700-900 vary from .82-.85 "allegedly"!!!