WW recommends 4000 over 6000. Hmmmm??

I've been researching my butt of lately trying to decide on which windows to go with in my house. I've debated me putting them in vs having someone else do it and although i'm capable of doing it myself the minimal price of labor vs how long it would take me to do it made having someone else do the install come out as the winner.
I've narrowed it down to Window World and one other local company. I know some of you out there don't like Window World and i've read all the complaints but i've done my research (lots and lots of it) and it seems most people that don't like them are their competitors and most people that are actual customers liked them and the windows themselves, which after more research come to find out are Alside windows which get more thumbs up than thumbs down.
So now that i've given you some background so this doesn't turn into a go with this window/company instead thread here is the latest question....
I wanted the salesman to find out if the 4000 series would meet the requirements for the new window efficiency tax incentive or whatever it's called, basically the window has to have a U-Facor of .30 or less (which some of you probably already know) He said that has obviously been something the company has started to research since before it only had to be .35 or less. He told me today that the 4000 will meet .30 if they do a different Low-E coating (nothing is in writing yet, but he said he will get with me as soon as it is) but that will raise the cost to $33 more a window. I can get the 6000 Series for $35 more which is their step up and he explained it as a heavier frame window that wasn't really necessary where I live (Central Illinois) which is why he still recommends the 4000. He said the 6000 is mainly used where the temperatures are extreme for long periods of time ie: Maine, Minnesota, Arizona, Texas etc etc.
So....... i'm still a little curious as to why he is recommending the 4000 over the 6000 since it will be more $$ for him and the company granted it's only $2 more a window x's 19 windows = $38 but hey money is money. Is he veering me toward the cheaper because he gets more of a cut or is it because he actually thinks it's overkill in my area.....
What do you all think????

 

I think you are probably correct about the profit margin being higher on the 4000 series.

Will the 6000 series get you to the right numbers without any additional charges? If so, I'd go that route if you like the look of them.

There may be install issues with the 6000 that I'm not aware of.

 

It's only going to be $2 more a window to go with the 6000. To achieve the U-Factor of .30 or below on the 4000 they have to put on more low-E or something which will cost an extra $33/window, whearas if I just go with the 6000 that already meets the .30 or below is $35 more than the standard 4000.
It just seems smarter to step up to the next better window since the cost difference is so minimal. His reasoining of still recommending the 4000 is it's a stiffer frame (wich in my mind would be a good thing, less chance of sagging/warping) and something about the aesthetics that the locks are different on the 6000 and you can see them better from the outside and with the 4000 you can't therefore giving it a "cleaner" look...

 

Sounds odd..the lower series has a stiffer frame? Thats not the way I read your first post. It may be that they insert aluminum inside the vinyl of the 4000 to stiffen the frame, but don't with the 6000 since it is heavier to begin with.

And most times, the higher end windows have the fancier low profile locks, wich normally are less visible and harder to defeat.

I'm just confused I guess. He should have miniature display windows he can show you to help you decide.

 

Whoops, I meant he said the higher 6000 has a stiffer frame, which is what he told me when I asked why he still recommends the 4000. He said it like having a stiffer frame was a bad thing..... I'm going to check it out more online I think.
By the way their 4000 is the same as Alside Excalibur and the 6000 is the same as Alside Sheffeld *sp?* Not sure if that will help but if anyone knows more about Alside hopefully they can shed some light on this for me...