For many, that is an incendiary question; as for some players tube amps are the only way to amplify a guitar. But solid state guitar amplifiers have been around since the mid-60’s and sooner or later they are bound to get it right. And in many ways they have.
As with many guitar-related traditions that are considered sacred, tubes were not used because they were better, they were used because they were the only available technology. As technology advanced, amp builders quickly tried to employ those advancements, mainly to save cost. For example, once silicon diodes became affordable, builders used them to replace the tube rectifier. It saved a tube, and simplified the input transformer. It was not a matter of sounding better, and in certain circumstances it changed the sound of the amp. And if you wanted more clean headroom, it actually helped.
Amplifier designers came to understand what made tube amplifiers so appealing, and the challenge was to make a solid state circuit emulate tubes. Fast forward to the last few years and this has been pretty successfully achieved both through modelling (digital signal processing) or purely analog solid state circuits. The vast majority of players today would fail a blind test between a tube amp and it’s Kemper-modeled version. And if you think about it, your pedal board is most likely entirely solid state, and your distortion is coming from a saturated transistor, op amp, or clipping diodes.
While players of means may insist on playing a tube amp, many players on a budget simply cannot afford a good tube amplifier. But that does not mean they have to settle for bad tone. Tube amps are inherently more expensive to make, and dollar-for-dollar a new $500 solid state amp is likely better and more versatile than a new $500 tube amp (if you could even find one). At lower price points there are some hybrid solid state amps with a tube or two in the preamp section. Whether that makes them better than all solid state, at minimum it’s a good marketing tactic (“it must be better, it has a tube”).
In my view, solid state amplifiers have been quite good for years at very clean tones (think Roland Jazz Chorus, Blues Cube) or high gain (Peavey, Randall, Line 6, Hughes & Kettner, etc.). When it comes to high gain there are lots of ways to do a great job (like your pedals) without tubes. Where tube amps shine is that in-between world where it sounds clean, with just a little bit of pick-induced dirt, crunch or compression: All those intangibles that make people love tube amps. But solid state continues to get closer every day, and at minimum there are many solid state amplifiers that make great pedal platforms, where you can chase the tone dragon with pedals (at more reasonable volume levels too). And frankly attempts to make tube amps “do their thing” at lower volume levels (like attenuators) have their own sonic thumbprint that does not always sound particularly natural either.
Solid state amps will probably always have a problem emulating the edge-of-meltdown sound and feel of a small tweed amp from the 50’s. Those are incredibly organic, tactile little boxes that were a happy accident of early amp technology. But most people don’t want a little tweed: They have very little headroom and don’t handle pedals well. It’s a narrow segment of players that want that, and for them maybe it’s gotta be tube.
Aside from the obvious benefits of solid state: Weight, reliability, cost….they do have some inherently useful sonic properties: 1) They are less prone to have a sweet spot for good tone. Many tube amps have a “just right” place where they sound really good (Everybody has had an amp that sounded anemic at “2.5” but was too loud at “3”). Solid state amps tend to be more linear and don’t greatly change character throughout the volume control sweep. Most solid state amps also have active EQ controls that actually boost and cut frequencies. Most tube amps are passive tone controls that only cut frequencies (10 on the dial is wide open, and from there you are removing frequencies). Active EQ controls are just plainly more effective (just ask your bass player).
I’ve been hauling tube amps to gigs for years, but my last gig was solid state for a host of reasons: It was a multi band night where we had to move gear around easily (weight, size) the room was hard and reflective, and the active EQ made dialing in a difficult room much easier. Plus any edge that a tube amp may have in certain situations is often lost in a noisy club. Or when the drummer starts.
Solid state amplification is now a choice, not a compromise. There will be players — especially professionals — who will always play specific tube amps. In many cases it’s part of their image…and they have roadies to carry them. You could give Yngwie Malmsteen a Roland Jazz Chorus and a pedal and he would still sound pretty much like Yngwie, just quieter. Much of the tone is in the hands.
Regardless of technology, quality materials, design and construction matter the most. Tubes are not a guarantee of anything, and there are as many lack luster tube amps out there as there are solid state. My philosophy is to find an amp with a really good fundamental clean tone knowing that I will likely use pedals for everything else. If an amp does not sound good by itself, no pedal will ever fix that. If technology allows me to get the tone I want from solid state, why not?