Yes the GFW is regional - i.e. there's more than one filter across the country. But the GFW actively monitors and blocks on content. This filtering and inspection takes finite time and hence slows everything down.
There is plenty of bandwidth. Accessing the same sites from Hong Kong is orders of magnitude faster. And BTW less prone to random errors introduced by clueless monopoly operators.
Perhaps you didn't understand how GFW works. The content is delivered to you after the RST signal, it's just the standard TCP stack ignored it. You browser may loading a page in half then suddenly Page-Not-Found, but if you have sniffer like tcpdump you can see the rest of the packets were still sent to you correctly.
Another phenomenon to help you understand the mechanism is that GFW fails from time to time. Why? Because the RST packets arrives too late.
HK has its own Internet infrastructure, it has nothing to do with mainland Internet. In fact lots of inner-China Internet connections are routed to HK then to the rest of the world.
The fact that RST is sent mid stream in no way lessens the point that the content monitoring leads to a narrowing of bandwidth which slows things down.
HK's Internet Infrastructure maybe its own but it is still this side of the Pacific and it is a lot faster to access US sites from HK than it is from China. And if, as you said, China traffic is routed through HK then the only difference is the GFW which is slowing things down.
Just because you don't see how it slows things down does not mean that it does not slow things down. The web in China is slower than the web in HK. Why? I don't know precisely because I don't have access to the GFW of course. Think of it as a funnel, the communication has to pass through the funnel so that the RST (or whatever) can be inserted. There's only so much BW in to and out of the funnel - so the traffic slows. The very fact the filtering happens must insert some delay.
I am sorry but I don't see any reasonable facts or explanation of how GFW slows the Internet down. HK is fast because your ISP is fast, it has nothing to do with GFW. I can download from ThePirateBay with the speed of 37MB/s in Chinese CERNET, and I can watch Youtube HD/HQ videos in ChinaTeleCom's 1Mb ADSL smoothly in midnight when the Internet is not busy.
I am a native Chinese living in China. And the tool I am using to visit youtube does not require any 3rd-party servers, it hacks into GFW and establish connections to blocked sites directly. :)
There is plenty of bandwidth. Accessing the same sites from Hong Kong is orders of magnitude faster. And BTW less prone to random errors introduced by clueless monopoly operators.