For bowl lathering creams, I actually prefer my Muhle synthetic most of the time. The newest generation of synthetics really hold their own against natural hair brushes, so much so that, I suspect that, in 20 years most brushes will be synthetics, and we'll only be using badger and boar for nostalga, not performance.

or, put another way, they're good now, and only getting better, so if you want a synthetic, go for it, just be sure to get a good one from a quality manufacturer.