The last few years I've been mostly using a Reeves 225, but for a long time before that I was a Sunn 200S/2000S devotee.
I still use the Sunn stuff, but for most applications the Reeves is easier to dial in tonally, plus at 24" wide it's easier to move and it fits better on a variety of cabinets. I have a personal pet peeve about that "T" look when an amp is wider than the cab it's on top of.
As we all know ratings can be deceptive. Factory ratings wise, at 225 watts vs 120-150 watts the Reeves is indeed more powerful, but not so much so that it makes a difference. Bass Gear Magazine got 256 solid watts out of the C225 on a bench, and I've never seriously scoped a 2000S under controlled conditions like the BGM tests, but I'm fairly certain that under the same conditions the Sunn would pull north of 200 watts.
BTW; I'll volunteer one of my 2000S's as a test mule if BGM wants to wring one out.
But, back on topic.
The big Sunns are awesome, and the Reeves is awesome on steroids. I like SVT's; don't currently own one but I have in the past and I undoubtably will again, but I agree that they are indeed the standard by which all other tube amps are judged. Also, it isn't a freekin' accident, or a conspiracy, or endorsement deals that cause so many pro's to use them.
However, as far as my personal "tone tastes", I find them tonally a little "soft around the edges" and sluggish with dynamic response compared to the 4 X KT88/6550 circuits of the Reeves and Sunns.
But... My favorite all tube amp is probably a 60 watt Sunn 200S; with a 200S cab. Certainly not big enough for every application, but suprisingly loud and at a reasonable SPL (it will get over a loud drummer) able to keep up in small-medium venue without PA support.
It just sounds so good, solid and rich you can almost taste it.