The blend vs single mountain debate is an ongoing one in the puerh market. There are a number of different arguments over this, but basically it boils down to “which one is better?”. The single mountain teas are generally produced by smaller factories. Sometimes it’s even by individuals. They often cannot afford the time nor have the resources to haul large amounts of tea with them from mountain to mountain, so instead they buy maocha at each place and then press them into cakes, making single mountain cakes as they go to each different place and collect tea. Blended ones, on the other hand, are more likely to be made by larger factories that have the ability to collect teas from far and wide and then carry them back to their factory to be mixed and then pressed. It requires more resources to do and thus are difficult for small producers to pull off, unless you are somebody like Chen Zhi Tong who spends a lot of time in Yunnan and who ultimately has the help of some big factory.
We have precious little experience of single mountain cakes aging — everything produced pre-1990s was blended. Expert opinion on the antique cakes (pre- Red Label) are divided, but generally speaking many agree that those are also blended — with different mountain teas, and not from a single region. So… there is a theory that single mountain cakes are no more than a gimmick for smaller producers to sell their tea. Just because a tea is from a single region has nothing to do with its quality being high or low, but somehow it is sometimes taken as such in marketing information or in consumer response.
Think about this: I think most whisky drinker will agree that a Johnny Walker Blue Label (blended) is going to be better than a poor single malt. It is not the most distinctive, but I think it does what it does very well — a smooth, enjoyable, and generally well regarded drink. There will be the malt-snobs who think any blended whisky is crap and refuse to drink such things, but that is more likely to be a status thing than anything else.
At the end of the day, very few of us (myself included) can say with any certainty whether or not something is blended. There are many who sell cakes that claim single-region status, and then consequently justify its existence by saying that single-region is better and pure and all that. There are also those who espouse the greatness of blends, how they are rounder, have less flaws, etc. If whisky is a guide, then what it really will be is simply that single-region teas are more likely to give you all the characteristics of that region, flaws and all. Blends will be smoother, easier to drink, and (at least to novices) tastier, but perhaps less interesting or less engaging for the devoted. Still, a blend made with top notch tea will always be better than a poor single region, and vice versa. There simply isn’t a quality correlation there.
And since whiskies are blended after they’re aged… what’s stopping us from blending teas after they’ve aged as well? Somebody told me he puts in a bit of very young puerh when he brews his wet stored stuff. It gives the tea more liveliness and makes the drink more interesting. I can certainly see how that’s the case, and there’s really nothing stopping us from doing so. Drink what you like, not what gives go status.