I came from the trading floor, AMEX. I never worked on the CBOE or ever traded in the crowd. I can't make any guarantee about which is better. I expect that the larger the order and the less liquid that strike is, the more value they add, but I have no proof. I think it's nice to have the ability to pay for "color" from the crowd and have them "shop" your order on their IM blast or over the phone. When I was on the AMEX, I was on the other side of the IM blasts and traded with brokers that way. Keep in mind that few trader view the complex order book. You will often trade with a MM that finds value in your order electronically from their values from what I call an "electronic eye" vs another customer that happens to what to do the opposite of what you want, or anyone that sees your order. By shopping your order, they can find on floor and off floor traders willing to play at some price, maybe no your price.
I don't have a current client that uses them. At my old firm, my firm did. They did a lot of volume through them and were very happy. Most of that volume was credit spreads is SPX or any spread in VIX.