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
Watts are not Watts. The reason tube amps have better Watts than solid state amps is pretty simple. It's because they generally have more dynamic headroom than solid state amps. Thus all things being equal tube amps won't clip as soon as solid state amps. Case solved.
Geoffkait,
How about Amperes, Volts and Ohms are they also better?
Ampere, Volt, Ohm and Watt were dudes that named these units of measure. I would suggest you to provide quantitative answer to your hypothesis by deriving your own unit of measure by how much of your units TubeWatts are better than SSWatts.
...but can you give algebraic or geometrical representation so everyone can understand?