In the latter case the casters will bear more of the backlash, or at least it will be split, so simply by virtue of not being alone in the criticism, it would be somewhat lighter on the players.

People here are advocating competitive attitude and scoffing at happy feelings in a game where Yogg is possibly the most appreciated card in the entire game and is encouraged to have a place in competitive decks. Hearthstone is a casual, feel-good game where competitive rigor comes 2nd; that's the very foundation of the game's success. I can see why the casters would prioritize a style aligned with the game's primary focus, because that is why most Hearthstone players are in the game and that's the identity they intuitively associate with HS.

Also, the opportunity cost is negligible. People are acting like missed analysis is lost analysis. However, practically a viewer is seldom missing out, because Twitch chat rarely misses informing of lethal. A non-astute viewer will probably miss out on a potential lethal in maybe 5% or less of games. So really, your second scenario needs the caveat that it will rarely ever be relevant.