Marvin Ultimate is a wood frame rather than fiberglass. Its more expensive than Integrity overall and there are mixed signals about the longevity of cased wood windows versus fiberglass or vinyl. Marvin is as a whole is very highly regarded tho and they are the producer of both lines. The Ultimates have more customization options over fiberglass Integrity. There is just some things you can't easily do with fiberglass as compared to wood. For example, our home is going to have some gothic arch top windows. I couldn't get them in Integrity and had to again go Ultimate for those particular windows. And believe me, they aren't cheap (probably due to the custom gothic radius). But the outer colors coordinate between Ultimate and Integrity so it will hopefully be a flawless mix. Windows aren't installed just yet or I'd post pics. I wouldn't believe white painted interior on the wood ultrex would be any less clean looking than all ultrex assuming whoever is painting knows what they are doing. I'd definitely track down a showroom and compare the two lines side by side. With the Wood ultrex its just a more classic looking window profile I think. The all ultrex is quite plain and almost, I dunno, cheap looking in comparison. Its definitely the more durable option tho, no paint to scratch (although the fiberglass can be painted) or wood surface to ding... Its a judgement call for you really. The Ultimate sliders come in 4 panel yes, in 10, 12 and 16 feet wide it looks like straight out of the catalogue. OXXO configuration so the 2 middle sections open to form one opening and net clear openings here listed in my catalogue lead me to believe if both are open, there is no obstruction in the center. The 12' wide one has a net clear opening value of 57 7/16" (or 59 for the non french door) The ultimate sliders have 2 versions..basic patio door and french door. The french door version has wider rails framing the glass, to mimic the look of a french door. The basic version has more glass area and thinner rails so if you go that route make sure you choose the model you prefer To throw more choices your way they do also have these in 3 panel like the integrity but in greater widths. I see here a 12' three panel as well if you just want one active slider but a little wider than the 3foot operator of the 9 wide integrity..lol What you should be looking for to find out how drafty these types of doors are in order to compare them to each other is air infiltration values. Unfortunately with Marvin these can be a bit of a hassle to come by but you could take numbers from a similar manufacturers slider and compare it to your lanai or bifold doors to maybe get a rough idea.

So here's the completed project with the Centor Blinds. Check out the install video at their website and realize that the casing that houses the blind assembly sticks out from the door unit a good 4-6" and looks shady onside- wish I'd taken a photo of that before having the left and right sheetrock furred out to make the screen flush with the interior walls. The mechanism slides well, but once in awhile makes a large "clunk" about midway that seems like it isn't lined-up straight on the reel-out of the screen side. I emailed Centor for care instructions, as I have a Phantom Screen on another french door that I silicone regularly, and they never replied. The only care instructions I could find were to keep the tracks clean. You see where the blind meets the screen, and there is a full-length magnetic pliable stip attached to make the connection between the two. It is so magnetic (most likely due to surface area of magnetic material, that t it is a STRONG two-handed separation to open the gap. I'm going to run some quality Scotch 32+ electrical tape at intervals to see if I can make separation more manageable. We have "lake" or "rice" flies that hatch at different intervals of the summer, and if they are on your screen or blind, they get crushed-into the material, and need to be removed via tooth-brush, etc. I'd do it again, but I'd check other brands to see if there is a comparable option that is US instead of Overseas-based.

This room has a standard 8' plate height. The door height is 6'-8" and the width is just shy of 15'-0". Our clients love it. There's a opaque shade that pulls all the way across from one side, and the other side has a one piece screen that can also slide over the entire expanse of the door. It's a great product! Good luck with your project!

What I know of WinDor from the commercial world is an average at best window, quite low on the food chain. LaCantina while not available in my area has a reputation of being a good product with good customer service/support. You may want to look at EuroDoor as well Jen. Have used them on a few projects recently with good sucess.