The short answer is that it's two completely different programs. Although both serve the same purpose, the way the Windows and Web versions conduct searching the Electronic Journal is completely different.
Here's some core differences between the two:
Speed, speed, and more speed - by allowing for the data to be stored in a SQL database, the search time is dramatically reduced.
One versus multiple programs - with ESCAPE Web, the program is centralized...meaning maintenance of the product is simplified. No more updating multiple machines which can be a time consuming process for some.
Improved functionality and search tools - ESCAPE Web has new functionality added to the query screens. Example: when searching the Transaction Text category, you are able to refine your searches by selecting whether specific term(s) "may exist", "must exist", or "must not exist". Using more specific criteria can narrow your search focus.
While the old Windows version is stable, ESCAPE Web receives all the attention for new development and feature upgrades.