My thoughts...
Electrolux/Eureka/Aerus has to be the most convoluted and confusing corporate history that exists. As an Electrolux newb, I found I had to ease my way into the sea of information regarding the companies and their products.
It doesn't help that there seem to be endless variations of the canister models over the years. They are all similar and there's a lot of information to juggle, so until you really commit to getting into it, it's all very confusing.
I currently have two tanks models. An Electrolux Ultralux 80th Anniversary with a VM3 motor, and a gold colored metal model which I understand may be a 50th Anniversary model. It's interesting, but for a while I guess Aerus/Lux continued with the body style that is now called the Classic. I believe this is when they went to the white and blue color scheme. The difference between those models and the current Classic, apart from the color perhaps, seems to be the wands, hose, and PN's were redisigned for a more modern look. I think this is when they went to the gas pump handle. Also, the Classic probably uses a different motor than those Luxes.
I guess after that they went to the style with the big box Hepa filter. I'm ambivalent about that styling. I like the clean look of the white and blue, but I agree there's something plasticky and cheapish feeling about it.
Now they have the three current styles that Dave was kind enough to post the documents for. One of them is the Classic, which is actually identical to my Ultralux (from what I can tell in the diagram), save for the color and perhaps an improved motor in the current vac. The wands and PN are the older style, with the metal lower half of the wand barrel. Interesting they went all the way back to this style.
I'm ambivalent about the other two current styles. The Legacy has that ramped hump. I think it looks a little to much like a van or an RV for my taste. The Guardian ULTRA, I feel, looks too cumbersome at the front end. Like a strange whale or something. And the silver on top seems like it will look shoddy once is get scuffed and scraped. Correct me if I'm wrong on that.
Having said that, I would jump on any of them if I found a great price.
I like the styling of the Classic/Ultralux a lot. I'm not too jazzed about the ultimate performance of the PN (the current Classic may have an improved brushroll though). I do really like my Ultralux a lot for bare floor and above floor cleaning.
I notice that Aerus gives a CFM spec of 145 for the Guardian ULTRA. That's a lot. It pretty much matches the CFM specs of a Sanitaire upright. There are no CFM figures given for the Legacy or Classic, however. Anyone know why that is? Incidentally, all three have the same Airwatt specs. Could the Legacy and Classic have the same CFM given the Airwatts are the same?