I'm neither, but I second this. 70/30 is a little too much fat for too little meat. If you cook it med-rare, there's way too much grease in each bite. If you cook it past that, the fat renders out fast and leaves you with a hockey puck. It could work with an egg in it and retain moisture up to med-well, though, I'd bet.
80/20 and 85/15 are my preferred ratios of ground chuck. These are doable med-rare or medium and retain their moisture.
I've been doing 90/10 lately, mostly since I need to lose some weight and still want to throw a burger on the grill once a week. Good, but it works better if I put a beaten egg in there to bind it. Otherwise it dries out fast.