Microsoft Office applications are not what would particularly be termed "Memory Intensive", so you won't see a big boost in the startup or
running of them...individually. If you are heavily multi-tasking, and have a large memory commitment, you may see some gain.
I suggest you download "Process Explorer" from WWW.Sysinternals.com
to get a good look at what is going on in the system. It is a Task Manager replacement that provides more data and explanation of Processes, etc.
IMO the biggest bottleneck in Application startup is the HD. But also IMO, startup is a minute part of application performance. If you are not
short on resources, don't close the application if you will be using it again...Minimize it.