I'm wary of any claim that any particular product is the "best ever" because it always depends on what criteria you're using.
That said, the M5906 is
very good if you want a heavy, thick, full-sized, complex, all-metal DA/SA automatic with a decocker/safety and a mag disconnect.
That said, the 92FS and the SIG P226 are also good choices, although their manual of arms are somewhat different.
Personally I feel the 3913/3914/3953/3954 are the best 9mm pistols out there.
I have to agree to some extent because they're
much lighter and more concealable. I also have a soft spot for the full-size and sadly short-lived alloy-frame single-stack M3903/3904/909.
At the time they were introduced I don't recall that they were great sellers or that there was a huge clamor for them. I recall a general apathy toward Smith autos...
They were expensive. They were big and heavy, with the possible exception of the alloy-frame single-stacks, although those weren't featherweights either. The DA triggers were never as good as the DA trigger on a K frame revolver, perhaps an unfair comparison, but an inevitable one. The earlier-generation pistols were flawed in some respects- the absence of a positive firing pin block forced 1st-gen users to rely on the clumsy slide-mounted safety, the frame finish on the 1st-gen pistols wears off if you breathe on it wrong, and some users found the blocky straight-backstrap 59-series grip frame to be
very non-ergonomic. The optional adjustable rear sight, although great at the range, is oversized and (let's face it) looks hideous when you're not aiming. Some buyers never did, and never will, get over an aversion to mag disconnects. (I like them, and I frankly wish my M&P had one, but I'm in the minority.) The list goes on.
Don't get me wrong- I like S&W TDAs, but I understand why many others don't.