I use different browsers for different things: let me fucking chose which browser to use.
I am currently wondering how easy it would be to build a "shim browser" that you can set as default but does not actually open the page, it only list the urls apps tried to open and lets you copy them to whichever browser you prefer.
Properly implemented such prompts would be great though. Someone else in the thread mentioned how location search results on mobile Safari always launch Apple Maps - it would be great to have the option to choose from whatever I have installed.