Quick pole: How many of the people advising against a 600EX-RT actually own one?
I ask because for years I have answered this first flash question and have always said get a secondhand 550EX, 95% of the functionality of the 580EX and 580EX II for comparative peanuts. But the game has changed, the 600 is the future. If you are finance limited then sure piss around with clones, I have. But the OP specifically stated they were happy to get a 600 if it was worth it, well I own one (actually three and an ST-E3-RT) and they are worth it.
Well yes, that's quick and dismissive. I've never owned a Stradivarius either, but I'd feel qualified to tell someone looking at getting into the violin that they don't need one. I never said that the 600RT is a bad flash, I'm just saying that it's overly expensive and pigeon holes you into Canon's RT technology. I get it, you own three and the command unit. I'm sure they're fantastic. But you're also in close to $2000 for a three light setup. You can do a lot with $2000 for a lighting setup.
The OP hasn't even tried flash yet. A lot of people hate it and don't want to deal with the hassle. Maybe he loves it; I'm just suggesting a more modest introduction to the art. Mostly though, I'm trying to offer contrasting opinion, because it seems the standard advice around here is to suggest everyone needs top of the line everything. Hell, I'm surprised nobody has jumped in to tell the OP that he needs to upgrade to the 5d3.
And yeah, sure, the OP said they were happy to get a 600RT, after people told him to get one. If you look at his first post he also says:
"I can afford a 600EX-RT, but I'm guessing there are features I'm guaranteed never to use, and that I'm better off spending money on several other units?"
"I don't mind paying more for more features, but if a flash has features I'm never going to use, I'd rather spend my money elsewhere (or on several flash units)."
The guy is looking for advice, so that's what we're giving him. I'm not saying I'm right, I'm not saying you're wrong. I'm just providing my opinion on the matter. Don't dismiss my opinions because I don't own the piece in question, we're not talking performance here like a camera, it's a set of features - features my setup has as well.