If you choose a platform that needs tools, if you give up the viral soft collaboration of View Source and copy-and-paste mashups and being able to jam jQuery in the hole that used to have Prototype in it, you lose what gave the web its distributed evolution and incrementalism.
You lose what made the web great, and what made the web win. If someone tells you that their platform is the web, only better, there is a very easy test that you can use:
When the tool spits out some bundle of shining Deployment-Ready Code Artifact, do you get something that can be mashed up, styled, scripted, indexed by search engines, read aloud by screen readers, read by humans, customized with greasemonkey, reformatted for mobile devices, machine-translated, excerpted, transcluded, edited live with tools like Firebug?
Or do you get a chunk of dead code with some scripted frills about the edges, frozen in time and space, until you need to update it later and have to figure out how to get the same tool setup you had before, and hope that the platform is still getting security and feature updates?