Exactly how much slower are you talking about???
After reading your post above, I spent about 10 or so minutes creating an example browser application using B4J, a text box and a webview.
After testing my app on a few well know sites, I must say that the speed does not seem that much slower than my usual chrome browser to me. When I say well known sites I mean obviously Google search results, ebay.co.uk, amazon.co.uk, ebuyer.co.uk, box.co.uk, youtube.com and a couple of others. Maybe it's because my internet speed is extremely fast and my laptop is no slouch either, but I really didn't see much of a speed decrease when browsing the internet on my laptop using webview.
I believe that webview will be slightly slower, but not snail pace slower as you seem to be getting.
What sites are you view???