...except....you fail to consider if he will ever actually NEED it.
By his own admission he only does light gaming, will he really need to future proof for a gaming machine?
Maybe. The fact is, nothing Apple's selling in laptops is really much good for gaming. "Light" gaming doesn't affect this. It's not as though the GPU comes with a fixed number of polygons it can render in a 24-hour period, and if you play for 8 hours you'll run out, but as long as you only play for 2 hours you'll be fine. "Light" gaming does not actually mean fewer requirements on hardware; it just means you use them less of the time.
A year or so back, I was asking people about the 335M that was, then, the top of the line. Ultimately, it turned out that it was, in fact, garbage. And as a result I ended up buying a Windows laptop so I can run video games, because Apple simply could not deliver an acceptable level of performance for ANY price. Heck, the 335M machine can overheat if you don't use third-party software to set the fans to run fast enough while running even older video games.
Now... If I were gonna get a new MBP, I'd get the 6750 one, probably, but I really don't feel like they've addressed the underlying issue there. I know, you can't get good graphics in a case that slim, so it's never gonna happen; Apple cares more about having the machine be really thin than they do about performance.
If you plan to play video games that are in any way modern, you should probably get the 6750 and resign yourself to sub-par performance. At that point, you may want to save the money, get a cheaper mac, and get a separate machine to play video games. When I priced it out, I could get a gaming machine with better graphics than anything portable Apple sells, plus a fast CPU, for less than the price difference between a low-end MBP and the cheapest one with the 6750M. (Okay, so it's one dollar less, and the gaming machine would be a refurb... Still.)
Basically, if you desperately need performance, Apple's laptops are not designed for you, because they are designed to be slim and light. That means they don't have enough heat sink material or airflow to handle the heat that would come off of a higher-end processor or GPU. On the other hand, outside of video games, almost no one actually has a use for that kind of performance; very little of the rest of what we do is processor-limited, and almost nothing but gaming is GPU-limited. There's $500 netbooks that can decode blu-rays to HD just fine; it's only video games that really use rendering hardware.
So...
Think through what you really want. If you're gonna be unhappy with poor gaming performance, find out whether the 6750M is enough to make a difference. If it's not, don't bother spending the extra money on it, because you'll still be unhappy. If it is, then it depends on what you were comparing with; if you're comparing with the 6490M, it's only $400, and that's not bad. If without the 6750M, you'd be fine with the Intel graphics hardware, then you may be better off with one of the much cheaper dual-core systems, and if you really wanna play video games, a refurbished PC will play video games just fine.
Yeah, having to deal with Windows sucks. On the other hand, so does getting <10fps.