Whereas other Fermentis strains, even if clones of famous brewery strains, are maintained by Fermentis.
W34/70 is the Weihenstephan strain and is QCed regularly to match the Weihenstephan strain.
W34/70 is the most used lager strain in the world.
It's the most common strain used in the scientific literature.
Schönram is one of the breweries using it.
Fermentis W-34/70 may produce satisfactory results for a lot of brewers, but not for me. Up until this pass through the hobby, I fermented almost exclusively with cultures I either received on slant or plated for singles and put on slant, which makes me a difficult customer to please. Everyone keeps talking about how great dry yeast is today, but the convenience factor must outweigh the small differences in the final product that matter to me. That is the nicest thing I can say at the present time. I just kegged a batch that I fermented with a direct pitch of Imperial L28 Urkel (which cost less than two packages of Ferments W-34/70 at my LHBS). My girlfriend who is completely new to brewing noticed how much smoother this batch was while still green than the batch fermented with Fermentis W-34/70 was after lagering. Both beers had the same gravity and were fermented using the same basic fermentation protocol. One beer came out of the primary drinkable. The other, well, I will be glad when the keg is empty. The W-34/70 batch still has a faint phenolic note and a definite lemon-like sourness, both of which my non-BJCP-trained girlfriend picked up on. Although, she does have an amazing palate due to decades of gourmet cooking.
I guess the moral of the story is that if Fermentis W-34/70 is working for a brewer, he/she should stick with it. However, until I find a dry lager culture that performs as well as liquid yeast, let alone as well as cultured yeast, I plan to stick to liquid and cultured yeast. Considering the small number of viable cells in an 11g package (at most, 55 billion for most dry cultures), liquid yeast is price competitive with dry yeast. I am willing to give Diamond Lager a shot because, even though it can be slow to start, BRY-97 is the sole dry culture I have used that comes close in performance to liquid or cultured yeast. Given the choice between the two dry yeast propagators, my bets are hedged on Lallemand at this point. Every brewer needs a "just in case" culture.