I meant to say I confirm your observation that class AB aren’t necessarily heavy tube amps.
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I look at three different factors and none of them are specifically Class A/B versus Class D. Specifically I look at weight, cost, and sound.
Here are some examples. I chose Fender just because I knew where to quickly find the weights…
$600 Rumble 800 HD
5.8 pounds
solid state preamp / Class D power amp
$1,000 Bassman 800
17 pounds
tube preamp / Class D power amp
$1,800 Super Bassman
65 pounds
tube preamp / Class A/B tube power amp
$600 (used) 1982 Gallien-Krueger 800 RB
23 pounds
solid state preamp / Class A/B solid state power amp
Recently I was looking at a Genz-Benz 250 watt combo that was Class A/B that weighed in at over 85 pounds versus a Fender Rumble 500 watt Class D combo that weighs 36.5 pounds.
All of that was just to give you a starting place on how the A/B versus D situation effects the weight and money.
Outside of amps with tubes, I wouldn’t expect to see anymore new bass amps using A/B instead of Class D. The advantages in price and not breaking your back, for most people, far outweigh whatever perceived difference there may be.
As for tube versus solid state. Where tube amps make electric guitars come alive, this isn’t always true for bass. Part of the reason solid state bass amps have proliferated over the last 40 years is because you can get a tighter, cleaner tone from them than using a tube amp. This, at least, is the theory. But you may still like the sound of a tube amp better.
For instance, the last bass amp Mesa Boogie put out was the Subway TT-800. It has a solid state channel and a tube channel that both run into a Class D power amp.
Having said all of that, let your ears be your guide and don’t worry too much about the technical side. If you like solid state, get solid state. If you like tubes, get tubes.
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Thanks everyone. So, if I have this right, in summary:
For bass amps:
Class A/B is your typical old school heavy analogue amp, which can also be a tube amp
Class D is your typical modern lighter solid state digital amp, which is never tubes
For pedals:
A usually means analogue, D usually means digital
What’s Better:
For all of the above, what is “better” is a personal preference, as like most things. 
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My only correction would be here.
All digital amps are at least partially solid state but not all solid state amps are digital.
In my example above, the Gallien-Krueger and all three of the Fender amps are analog but only the GK 800 RB and the Rumble 800 are solid state analog amps.
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Now I’m confused again. 
The Rumble 800 and Bassman 800 are Class D, but you are saying they are analogue?
Just glanced at this article and I ran away screaming. @DaveT would probably love it though. 
Maybe I should just stick to what sounds good to me and not worry about the Class.
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That’s always the best way, as you have to enjoy the sound of the complete setup first, shouldn’t you?
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class D is only for power amps, so it’s irrelevant in a pedal when a pedal claims to be “class A” it usually means that it’s made with discrete transistors and not operationnal amplifiers. it doesn’t mean that it’s better.
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Just marketing then? “Class A” does sound better for people like me that don’t have a clue. An A grade is better than a D right? 
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Yes. I completely ignore the circuit architecture when making choices.
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Quality is quality regardless of pieces.
About 15 years ago I worked with a powered studio monitor manufacturer. We couldn’t put class D amps in the monitors because the recording industry wouldn’t accept it. We did blind comparisons and nobody could identify which amp was which, but the myth was out there and we had to accommodate it. In the very early days of class D they had problems with high frequencies and that perception was hard to break. Even then we used the IcePower class D module in the companion subwoofer. I think we left the amp specification off the data sheet and people maybe assumed it was the same as the mains. Class D was a good bass amp from very early on.
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