I love the Xiaguan red flame. I've never had the bing version, but had brick version and traditional mushroom version. The mushroom ages very well. The last time I tried it, an 2006 dry-aged mushroom is already very drinkable (to me). I also have a 1997 dry-aged mushroom that's surprisingly good (to me) and keeps me ever wondering whether post-2000 mushrooms can age so beautifully too. I think the mushroom version is much better than the brick version. But the brick I had was pretty enjoyable too, for a price almost like free
I very much believe the processing of mushrooms is significantly different from that of most other sheng, but haven't yet found out the details yet.
I think the Xiaguan mushroom is a classic of cheap great sheng. But I don't know what's going on with the recent year mushrooms with fancy packaging and much higher price.