great question. It always depends on your requirements, at a company level.
Functional speaking, does not have a requirement, per-se, but there might be important considerations that might change your mind in that sense:
- Support from SAS: level A support is about to finish, if not already.
- Support from your OS provider: SAS 9.3 do not officially support several of the new Operating Systems, hence you cannot upgrade, which will make you lose the level of support also of your Operating system.
- Security: indeed, since the level A support might be outdated, the newest and best fixes and patches might not be available for your versions of SAS and the Operating system.
What SAS solution or products do you have installed and what operating system, and their versions?
In terms of security I can't help, your SAS rep would be best placed to answer specific questions there.
In terms of this: " Is there a big jump of what SAS 9.4 can do versus 9.3?" - yes there is a lot more that 9.4 can do, and it is being added to regularly. One big difference is the libname excel/xlsx engine in which you can read/write native xlsx files, rather than in 9.3 where you create tagset output.
One of the major hurdles to upgrading, which may or may not affect you, is the bitness of the OS. Catalogs written for 32bit have no upgrade path to 64bit, they need to be recompiled - or as a better method not stored as catalogs at but use nice portable open text files.
Also, and since you mention WRS, and Model manager, it seems you have also middle-tier/web applications.
The web tier is also very much improved in performance and maintenance. Now you won;t need to install your own Web Application server (JBoss, WebLogic, WebSphere), but SAS comes with one of its own, so very standarized, and Apache comes already out of the box with load balanding and other enterprise level features.
Finally, in 9.4 you have also the change to bring your WRS reports to nice SAS Visual Analytics reports. Probably VAAR ( a reduced version of VA) would be available in your solution. You can check this with your SAS account manager.