One big downside to broilers is that they are a lot less flavorful. Part of that is because so much of them is white meat (breast), and that by definition is less flavorful because it's so lean and dry. Part of it is because broilers are too heavy and disfigured by their breeding to be able to move like a real chicken does (even if they had the space), so they tend to sit around a lot, and muscle that's not used is less flavorful. And another part is the extremely young age at which they are butchered - it makes for tender meat, but it also makes for less flavorful meat, because it hasn't had the time to develop flavor yet. So you pretty much sacrifice flavor for tenderness. I personally prefer flavor, and dark meat, so I don't like broilers. But that's just personal preference.
Resting the meat seems to make more of a difference with older birds. I did an experiment a year or two ago, where I butchered cockerels of the same age and dual-purpose breed (4-5 months old or so), I rested one for a couple of days and didn't rest the other at all. Cooked them the same way. Found no difference at all.