If you already have MRQ2, IMO opinion there's less incentive to buy the Legend Core rules. I already have the MRQ2 core rules. I probably will buy the Legend Core rules anyway for the following reasons:
1: It's only a tenner
2: it's a smaller A5 format, so can stick it in my bag easily to read on a bus, train whatever.
3: The rules are apparently getting cleaned somewhat. I'm told Charging is better clarified.
I have to say tho the price is the main reason I'm buying it. A Tenner is a bargain. There's not much in the way of RPGs (in a physical book format) that you can buy for a tenner brand new these days. A tenner brings it right into the realms of an impulse buy.
I probably WILL buy RQ6 as well, just for curiosity, depending on the price.