Tube Watts vs. Solid State Watts - Any credence?


I've heard numerous times that Tube watts are not the same as Solid State watts when it comes to amps running speakers. For example, a 70 watt tube amp provides more power than a 140 watt solid state amp. Is there any credence to this or just sales talk and misguided listeners? If so, how could this be? One reason I ask is a lot of speakers recommend 50 - 300 watts of amplification but many stores have 35 watt tube amps or 50 watts tube amps running them. More power is usually better to run speakers, so why am I always hearing this stuff about a tube watt is greater than a solid state watt?
djfst
A worse amplifier has higher dynamic range? Worse how? Because it clips easier? And therefore has more gross distortion at volume? Because it has less dynamic range? Worse it has an order of magnitude higher THD than the "better" amp? I see where this is going. :-)
You educated guys now totally confused the hell out of me.
So what should I want? Class A 500 wt/ch tube amp?
One strike against Class A tube amps in particular is their very high cost, has anyone actually checked out what a good 100 Watt Class A tube amp goes for? Hel-loo! One assumes you're NOT referring to milli watt SET headphone amps, not that there's anything wrong with them as all.
Mapman, my point is that without further information one doesn't know whether to view a "good" dynamic headroom spec as the glass being half full or being half empty, so to speak.

And my perception over the years and decades is that a "good" dynamic headroom spec often (although not always) correlates with lesser quality (and less expensive) designs.
Is there an amp not capable of putting out more power cleanly for a shorter period of time?
Most well designed class A amps would be good examples, as Ralph indicated. In fact with a class A amp, as I understand it, the more power is continuously delivered to the load, the less power the amp will dissipate internally, and therefore the cooler it will run internally. Which suggests the possibility that in some cases a class A amp might even be able to deliver slightly more power continuously than briefly.

Re your last paragraph, I would certainly concur.

Best regards,
-- Al
"Class A 500 wt/ch tube amp?"

That should do nicely if you can afford the power bills. Doesn't Ralph have one of those?