Why is that? What is it about them that makes people trust their recs more than the others? Is it sheer volume? Ease of use/ability to find what you are looking for (PJ's theme lists)?
Y'know, I don't really know - but to guess, maybe because they started out back in the day when there wasn't so much fic, weren't so many fen, weren't so many comms and events ... they became household names. I think it's harder to become a household name when the household's bigger. I do think to an extent PJ's genius (I don't think that's too strong a term) for organization helped. :-) Also maybe the people who say "switch" and "PJ" are old-time fen? I kept up much more 5 years ago than I do today; that plays into who you think of when someone says "Snarry."
And I should add that though I think of both switch and PJ as champion reccers, I was never one to actually read according to anyone's recs *g* because they never seemed to rec stuff I preferred. :-) So recs never helped me much anyway - I still had to simply read stuff to find what I liked.
Now, again, that (and reccing, too) was easier when there was less stuff. Snarry is so big now that I think a lot of things, one of them being any real ability to get a valid pulse of Snarry and name the "best" stuff in any coherent way, are almost impossible.