I would like to know if it could be a problem to work with a SW2014 in SP2 and another in SW2014 SP5 (the work files being available on the 2 workstations). Then I looked at the release notes on the internet: http://files.solidworks.com/Supportfiles/Release_Notes/2014/French/relnotes.htm Nothing is really detailed about what service packs bring?
No particular worries, but it's advisable to work with the latest version, especially if you already have the installation files (because the most boring thing is the download) !
The update does not change anything on the computer, and can be launched one evening!
The link you give only shows the improvements, but not the bug fixes!
Edit:
A random example found on the SolidWorks KB of a bug fixed in 2014 SP5 (so still active in 2014 SP4 and earlier):
SPR #:815034 Product:SolidWorks Status:Implemented Fixed in:2014 SP05 Area:User Experience (UX) Sub-Area:User Interface Customer Impact:Medium Enhancement:No Summary: User Interface: Context toolbars" "Show quick configurations" and "Show quick mates" are disabled by default
Or:
SPR #:830346 Product:SolidWorks Status:Closed (Implemented) Fixed in:2014 SP05 Area:Assemblies Sub-Area:Open - Assembly Customer Impact:High Enhancement:No Summary: Performance: Open - Assembly Performance: Opening large assembly in large assembly mode takes 25 minutes compared to 2 minutes when large assembly mode is disabled (assembly specific).