I'm on the same search as you and have a spreadsheet with 26 different models on it. Consider American Standard with the Champion 4 flushing system. It has a 4" flush valve (May be the largest in the industry) and a 2 3/8 trap with a 10 year warranty. Clogs should be a thing of the past. They have many different styles and a few that are 1.2 GPF

Keep in mind that the pressure assist models tend to work a little better with less water, but are a lot noisier than the gravity flush. Some of them actually startle you when you flush. That's bad for night time visits to the water closet! :0)
I have several links for you from a Ca website. This is a link for toilets specifically, but the site covers all kinds of items.

Here is a link that might be useful: CUWCC

Here is another. Testing updated this month.

I really want a dual flush, but MAP testing show them not performing that well with solid waste???

Here is a link that might be useful: MAP testing

We got a Kohler Cimmaron that our plumber stocks. I'm not certain which flush variation is was, but it's a newer one, not the old standard. We've had it several months and are quite happy with it. No problems with the flush other than getting used to a different sound.

DS is having some issues with him toilet upstairs and I think we could be putting another one in up there before long.

My neighbors who are interior designers and work in a fairly upscale home goods place in our town, swear only by Toto toilets. They sell a ton of brands, but those are the ones they and the plumbers who work for their store really like. They put Totos in their house, so that is what we bought. I read up for about a year on stuff for our upcoming bath remodels; keep reading good stuff about Totos. The higher end Kohlers can be good, but you can also end up with issues as well, not as consistant with manufacturing. Regardless of what you do end up buying, I'd buy from a plumbing supply, not one of the big box stores.

For us, we went with Toto Promenade for both of our upstairs baths, the newest G-Max flush models which are also ADA height - not the older models and will be using a Guinevere or Soiree in our downstairs bath.

Have a look at the Caroma toilets. I'm Australian, and we have had dual flush/water saving toilets for nearly as long as I can remember. I've never known one that clogged.

The toto Aquia dual flush also looks pretty good, and is reasonably budget friendly

Here is a link that might be useful: water saving toilets

Add to list of possibilities/seeking reviews for:
Toto Eco Dartmouth
Toto Eco Whitney
Toto Eco Promenade

Right now I'm leaning toward the EcoDarthmouth for size reasons.

Toto wrote the book on low flush QUIET toilets, and they have a wide variety of models. We have two of them and they work very well. I believe they have 3" flush valves which means they rarely clog. However, on those very rare occasions when they do clog, unclogging them requires a much more vigorous effort with the plunger than I remember using with a toilet that was not low flush. Given this observation from our experience, I wonder if a toilet with a larger flush valve is a better choice. Maybe so, but only if I had assurances that it is as quiet as the Toto. Maybe Toto makes a toilet with a larger flush valve.

BTW, the Toto soft close seat is worth the extra cost.

Aren't you doing a vintage-y bath? You might take a look at Kohler's Sterling brand -- I think they have 1 or 2 ADA-compliant dual flush toilets (.8/1.6) and to me the styling works well with that vibe.

We just installed the Kohler Sterling Rockton a few weeks ago and are quite happy with how it does its task, but it sits too low to meet the 17 - 19" ADA standards.

I will say my plumber uses Toto in his house and I've heard good things about Caroma.

Re the American Standard Champion water saving toilets. We installed 2 last year and this year one of them started to have an internal leak that was getting progressively worse.

Long story short, they are very customer responsive. I just called up their customer service and within 48 hours I had the replacement part delivered to our home.

Oh, one more thing. About 6 months ago they changed completely the flush valve. This tells me that it wasn't working, we weren't the first to complain, so they changed the design completely. The white components (with the orange seal) have been replaced with totally different grey component (yes, singular) wiht a green seal.

It works great.

Dan