It sounds like you are asking about mulled units (whether done in factory or on site) compared to individual units installed within the homes existing wood mulls? Is that correct? If so, it is really a matter of preference. A mulled unit will net you more glass area and a streamlined appearance, as well as minimize the areas for potential air leakage. Leaving the wood in there and installing individual windows preserves some character and some people prefer that... If your question was in reference to factory mull vs field mull, I'd concur with the other pros, no difference. There is a size limit that most manufacturers have for shipping purposes, however it is FAR more than 52".

I have a nice large sliding window over my kitchen sink, so I have a center divider lined up over it. While I have learned to ignore it, I think it would both look better aesthetically and function better for viewing if that center divider were not there. I agree it's not the end of the world if you can't change it - but if you can and it doesn't break the bank, I would. However so many others here have already weighed in saying they have it and they don't even notice it. So this is going to be one of those deeply personal things only you can answer.

Hi @nehome. I know it has been 4 years but on the chance you're still around, I would love to see the result of your mulled Andersen Woodwright windows. I am about to order our windows and our order will include three 2-wide double hung mulled units (one over kitchen sink, one to replace a picture window in our dining room and one in a bedroom. I am trying to visualize what the mull will look like on the interior, The image on the quote is the exterior view and shows several different measurements, one appears to be the width of each window, ie. 23 3/8, the other is the RO width (47 3/8) and then the unit width is 46 7/8. 23 3/8 x 2 = 46 3/4 so I guess that means the mull width is .125 but this seems really narrow. I must be missing something.

Done all the time. Andersen sells Narrow Mull Kits for just this purpose.