As crazy at it sounds I went and bought an X-Surf 100 card and a Rapid Road module for it. I was using the Mediator with Spider 2 USB and a PCI Fast Ethernet card prior. Since I sold a couple non Amiga related items and had the money in paypal I figured what the heck and want to see if speed tests were any different.
Meditor Fast Ethernet Driver with Roadshow is slightly slower than the X-surf 100 card. Its hardly noticable at all. So its not the hardware slowing things down.
I also have an 060 with my network device optimised for it, so again not really software as far as TCP/IP stack goes. MEdiator driver and the x-surf driver are both optimised to take advantage of Thor's MMU lib package as well, booted with and without it and didnt notice any significant speed differences.
My system is an A4000T with a Radeon 256MB PCI card, csppc accelerator with an 060, I have over 600MB of fastram free when launching browsers.
Aweb, Voyager2, Ibrowse are all extremely fast in comparison when visiting simple HTML based sites. NetSurf still takes between 25 seconds at best to as long as 2 minutes to load a page.
Just for kicks I booted from a partition that still has MiamiDX and it was even slower than Roadshow, but I knew that. I also installed AmigaKits EasyNET that came with my x-surf 100 and it was slightly faster than MiamiDX, but not faster than Roadshow.
On an emulated system that I have setup as close as I can to my real amiga, using a backup of my current drive and WinUAE bsdsocket emulation its WAY faster, so I am at a total loss here.
The only thing I havent tried is to install 4.1FE classic on my A4000T and see how it runs, but thats a totally different version of NetSurf.