He wouldn't be downgrading in anything except for the resolution. The new 15 cMBP has identical specs minus the SSD and RAM. Not to mention that at least it is upgradable...
Anyhow, OP I would not dare put a Anti-Glare film/screen protector on a RMBP as Anti-Glare films tend to make the screen fuzzy and ruin the point of having a extremely high res screen. I had a Anti-Glare film on my iPhone 4 and it made the Retina Display look like ****. On the other hand, the Anti Glare MBP you want is fantastic. It keeps the sharpness unlike the AG films. So if you want a Anti-Glare MBP go for the High Res Anti-Glare MBP. You can put a after market SSD and RAM in it for a hell of a lot cheaper than what Apple charges for them. I would also say the cMBP would be more future proof due the the ability to upgrade. Either way I hope you are happy with your decision

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There is a difference. AG films do much worse the more there is between the panel and the matte film which is usually one of the top most layers of the film.
The iphone has a glass cover that is bad for ag films. The Retina screen does not which makes it much more suitable for a ag film with good results.
Also there are some really poor ag films like the ones you can buy in some at&t shops. The easier a film is to apply the worse it is. It needs to be very thin and stick very tightly with as little adhesive as possible.
I once used the ARM200 from Vikuiti (3M). Which was pretty good there are similar ones out there.
You probably won't get one in 1 week to try it but in theory you can apply such a film and remove it again without any residue. Actually removing it is like cleaning the screen perfectly of any little dust particle.
Next to the RMBP price tag those films are cheap 30-50$. If you manage the time problem somehow you can just try it.
As for the link of klex
Easy to install without air bubbles
Some screen protectors can be a hassle to install - but not this one, as it is quick and easy to apply without the fear of trapping air bubbles.
If this is true (they all say it is easy to apply but that is rarly true), it is a crap film. At least my research on the matter showed that when I compared different ones for my Samsung a few years back.
I would get the 3M film. You need to check google for resellers that sell them precut. The 3M homepage links some too I think.
http://solutions.3m.com/wps/portal/3M/en_US/IndustrialFilms/Home/Products/ProtectionFilms/
Those are very good and from the source so you know what you get.
Most company just buy them from 3M or similar companies and put their own label on it.
For example I guess the viewguard is just a 3M film sold under the brand of that company. I doubt viewguard has the know how or resources to make such a film themselves. All the do is cut them into the right shape and form. Package them and sell them.
http://www.notebookreview.com/default.asp?newsID=5753
http://www.viewguard.com/en-us/
You need to find one reseller that cuts them into the right shape that includes the whole black border. After that applying it should be somewhat easier than with notebooks that don't have that border. The result should be as good as can be with an ag film on the retina MBP. Much better than on the glass covered stuff.