The Radeon Pro GPU is similar to AMD's former FireGL line. It's designed for applications like Maya, Final Cut Pro and Photoshop. It will work for gaming at moderate settings; but it's tweaked to do more "work" than "play" (cue "I'm a Mac" commercials and "Hey PC, doing some work? I'm gonna go have fun", whoops!)
First off, do you need a laptop for gaming? Mobile components, CPU's and GPU's especially, have to confine themselves to certain heat and power requirements, to do so means cutting performance. Even if the numbers are identical, they aren't identical. For example, a "GTX 970 with 2GB of VRAM" you'll see on the label of a Windows Gaming laptop is far slower than a "GTX 970 with 2GB of VRAM" desktop card in a desktop PC. It's all just marketing. Gaming laptops are both more expensive AND slower than their desktop counterparts. Now, some people need a laptop; I get it! So if a Laptop is what you must do, then go for it!
If a laptop is what you must do; then a Windows gaming laptop is a far better value. To be honest, if you want a MacBook Pro; then you should have a reason to want a MacBook Pro. You need portability and want certain Mac Apps to work as well as possible (I ordered the 15" for Final Cut Pro, for example). Or maybe you just love the industrial design, ease of use and reliability; and that's worth the money for you. But if you're buying a laptop to play games on, a MacBook Pro simply is not the right tool for the job. A Ferrari and an 18-wheeler with trailer cost about the same amount of money. If you're hoping to win your next track day, the 18-wheeler isn't gonna do it. If you're hoping to branch out as an over-the-road trucker; then the Ferrari isn't going to get you very far. You need the right tool for the job.
Depending on your needs; one option might be a 12" MacBook or a 13" non-touchbar MacBook Pro, AND a Gaming Desktop; for about the price of a 15" MacBook Pro. You've got a Mac for Mac stuff that you might want to do; and a gaming PC for gaming.
NOW; if you NEED a Mac for some specific reason. For example, Final Cut Pro, or developing for iOS, or whatever. And you're buying a 15" MBP for that reason? Then it makes sense to get the 460 GPU; and then you can do some light duty low-to-mid-settings 1080p gaming in your spare time.
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Better than your HD4000 setup. Not significantly better, but better nevertheless. When it comes to me and my laptop, I want a Mac. I also like to play games. I game on a Windows PC. But I didn't mind paying more for the faster GPU both for the "Mac Stuff" I want to do; but also to be able to play games occasionally, like you, perhaps when I'm traveling. It's all about expectations. The fact that my Mac is powerful enough to play most games at reasonable framerates at reasonable resolutions is icing on the cake. However, I'd be sorely disappointed if I bought it expecting to get a "gaming laptop".
For the record, if you can spring it, the 15" Model (Quad-Core CPU and Dedicated GPU) is significantly more powerful, and will be much better for those occasional games. IF you can stomach the pretty substantial price.