Ah, the old tube vs solid-state debate
Just stating a blanket statement on comparing tubes to solid-state, you're giving the tube camp an unfair (technical) advantage already, and we have not yet begun. Without getting into the measurements, even/odd distortions, etc... I'll try to point out a few points in order to try and "normalize" the playing field somewhat. At least, a prospective buyer can be made aware in order to make fair comparisions on tube vs solid-state equipments. Let's start with tube being simple device where the implementation parameters are more strict in terms of the circuitry it's going into. The underlying pre-requisite for a tube circuitry must start with stable (beefy) high-voltage input power-supply before a decent tube circuitry can be realized. It is here, the high-voltage input power-supply, that most consumers overlook as the biggest advantage of the tube offering, hence the hidden "unfair advantage". Solid-state devices are more forgiving in the sense that one can get a reliable circuitry, yielding decent sound while reducing the cost of goods by skimming on the power-supply section. This "decent" sound is good enough for the mass market where cost-of-goods is the name of the game. If one were to pay close attention to the meticulous details and put a good power-supply into a solid-state circuitry, one can get excellent sound from it as well. There are many solid-state implementations with good power-supplies rivaling the tube counterpart, Pass Labs, Rowland, Mark Levinson, Monarchy Audio, to name a few. When comparing these products against the tube counterparts, say Cary, Audio Research, VTL, one is hard-pressed to say which one is "better" technically. One may like one sound over another, but that is strictly a personal preference, not based on any technical merits at all. It all comes down to whether one like the warm romantic or the more transparent, accurate sound. For example, one may prefer the warm, organic signature of a classic Steinway piano, where others may look for the crisp, modern sound of a Yamaha. Now, that is a fair comparision in my book. On the other hand, comparing a tube integrated amplifier with a solid-state receiver is more akin to comparing a piano with an electric keyboard, and I don't think the cheap electric keyboard is a good representation of what a professional one is capable of.
I myself am on the "dark" side where I need the glowing tubes to provide some enlightenment (pun intended), but I have heard my friend's system with Pass Labs equipments and it's very impressive. I all comes down to your preferences, so as Roberto always says: "Trust your ears".
Spike