Marvin windows have the reputation for being among the best for historical reproductions. I believe they make true divided light windows. We have Weathershield windows, simulated divided light, and they look pretty good, but not great.

If by "plastic dividers in between the pane layers" you mean "between-the-glass" thin fake muntins, there are other options that look a lot better.

The most popular these days is the Simulated Divided Lights where there are standard split muntins glued to the outside and the inside of the insulating glass. There is usually an option to install a dark or light "spacer" between the panes that aligns with the muntins so you can't see through the space between them when standing close to the window.

It will be difficult to meet the u-value required for the tax credit with single pane Authentic Divided Lights. Check with a Marvin supplier to see if their single-pane sash with an "Energy Panel" qualifies. The energy panel is a glass panel attached to the outside of the single pane authentic divided light sash with clips sort of like an integral storm window. I believe they make it with a Low-E coating so it might qualify. I'm not sure if they make it for aluminum clad windows.

By the way, some of the Simulated Divided lights don't qualify for the tax credit with a spacer between the glass panes.

There is no such thing as a happy Historic Preservation Society but they typically care little about energy conservation since historic buildings are usually exempt from energy codes. I've used the single pane Marvin to satisfy them and then installed the energy panel later. These people will sometimes insist on single-pane glass and then allow a standard aluminum combination storm window on the outside because the non-historical effect is "reversible".

The best historic window I have seen is made by Boston Sash in N. Deighton, MA. It has a balance mechanism hidden in the side of the sash so it is virtually impossible to tell it from a 100 year old window. It does not meet any energy codes or qualify for a tax credit and it has no cladding. It is allowed in MA as a replacement for an original single-pane window if there is a storm window of some kind.

Is there a reason why you don't keep your existing windows? Are they original? If so, why not just add storms and use the tax credit for that? It would be the green thing to do and the best fit for the house.
Diane

Oh yes, I would have LOVED to have the original windows in my 1924 bungalow, but unfortunately the owner in 1980 did a Home Depot remodel of the whole house, and the 1980's windows are starting to fail. I wanted to go back to looking like a bungalow. Unfortunately, I am in California and all remodeling, including window replacements, has to comply with title 24 (energy efficient). The plus side is they'll qualify for the tax credit that way!
And I think some of the Marvin windows might work, if I could only figure out their prices!
Thanks!
Carla in Sac

Carla, you might also see if there are some local window shops that will make the windows. I know there are several that do this in the Bay Area, and it's less expensive (for most of them) than the equivalent Marvin windows. The downside is that they don't qualify for the tax credit, though, because they aren't NFRC-rated. (But they're fine for CA code.)

Locally, it's Marvin windows. Gorgeous, but at $800-1000 per window was out of range for us. So we kept the original windows. May put storm windows or outside shutters up. It's difficult, because otherwise we're working to make our house very energy efficient, so we've done the best we can, but kept our original single pane windows :(