I'd prefer closed tsumo, m'self. But, it's something for me to depend on. I've yet to get a good feel as to what tiles might be left in the wall to get a gauge on it. At the same time, I'd rather lose points by tsumo.
Points by ron, you get a net difference. You gain points, while an opponent loses points. At times, y'won't need a baiman tsumo, when a mangan ron will do just nicely. It is this point swing, that drives me to prefer points via ron at this point. Of course, the major disadvantage: it leaves all the other players alone.
I have to admit. During Live Tile games, I tend to forget accounting tsumo as a yaku when counting the points up.