If running a few projects that only employ the basic page bank processing and likewise few branch shortcuts, then v2.4.2 will probably serve well. It's not clear whether v3 improves OSA support since you have to turn on legacy 2.4.2 support to get it to connect to JDE OW.
Clustering Support is better in v3. FormScape Administrator (new) provides better change management capability. It does not have a true change management package; it just has better tools in the developer with which to adhere to good practices. For example, the security access managed by the FormScape Administrator, a good idea reasonably well implemented. Also within the Administrator are better branch log monitors. Unlike the old log.txt file, which logged everything into a single file with a size limit that automatically truncated the file when its maximum is reached, it now keeps separate logs for each active branch process with inbuilt search capabilities. CAVEAT: none of the new logs are automatically deleted; they just get closed and a new one is opened every 24 hours. So every so often you need to delete them for yourself manually or create a DOS batch process to delete them or something to that effect. The developer has tabs replacing window tiles, a great improvement over the old. The development environment has enough look and feel like the old to be familiar yet new features that may require some effort to learn and manage.
If the maintenance contract is current, then get it even if there is an additional cost. And if needing clustering support or are doing clustering, then v3 is probably a must have. Overall, it is a plus to get despite needing to re-learn the Developer.