No idea, are there five? DxO seems to be not bad for lens tests.
I just Google stuff and troll forums I find. That way it takes a lot of the ads out of the equation. Most any site will have some kind of bias so filtering through human interaction is very useful. I glean information to make many decisions about hardware and useful practice that way.
DxO is decent, and DPReview works with them for their review data, but I find it best to approach all of them as if they're outright liars.
My lowest bar is whether or not Lensrentals carries it- if Roger thinks it's too bad to be rented to a customer for some reason, it's too bad for me. You can also look at his 'Roger's Takes' on various equipment they rent to get an idea of what a part is good for; just don't expect overly negative comments.
Ken Rockwell is a bit pretentious and a bit of a fanboy of whatever he's shooting at the moment, but he'll tell you if it works (if he can make it work, for work).
Photozone.de seems pretty decent and has been good for comparing lenses between reviews, and I've used their data to map out my lenses- what aperture is sharpest at what focal length, etc. Still need to find a way to relate focal distance to all that; maybe I'll find a pattern I can use.
Otherwise, there's a smattering of sites out there and each has their own forum, and I really haven't developed a real preference, other than reading a lot of them when I zero in on an interesting product.
On a more interesting note, my Grandfather pulled his Circa 1981 Minolta XG-1 SR-mount 35mm film camera out of the closet, along with Minolta/Rokkor 45/2 and 50-135/3.5 lenses. Says the camera needs a professional dust-up, and the lenses look good to me, so I'm going to take the body by a shop on Monday to see what they can make of it. He's in his eighties, so I'd love to get the camera shooting (assuming it doesn't shoot now) and get some shots of him and family blown up with it.
Worse comes to worse, I hear Minolta SR-mount adapts very well to mirrorless systems, including Fuji