There are three factors to consider when choosing or switching eDiscovery solutions with respect to the number of cases being handled.
The first is the number of cases you are managing simultaneously. If you're only working on one eDiscovery matter at a time, remembering where you were and getting caught up is relatively easy. If you're juggling more than one matter, having a platform that helps remind you where you left off and tracks what you have done thus far is imperative. For instance, if you're working on redacting documents and are interrupted to take care of something else, reviewing the redactions you performed by looking at them in see-through mode when you come back helps identify where you paused.
If you have a litigation support team or personnel who spend most of their time on eDiscovery, a solution that can handle dozens to hundreds of cases of all sizes is critical. Furthermore, it must be easy enough to navigate such that a range of users, from those who simply want to review documents to power users handling exceptions and regularly creating tricky productions, can accomplish their respective tasks.
Second is the number of cases that you add to the solution on a regular basis. Having a tool that you can use for other tasks while also loading data is very important if you're processing several cases at a time. That way, you don't have to wait until data loading is finished to begin working on a case. Even if you only add cases a few times a month, the loading process needs to be streamlined and simple.
The third factor to consider is cost. If you have one matter at a time, using a full-service vendor might make sense since you're passing the cost through billing it back to your client. Having multiple matters allows you to offer your clients a discounted price over individual project pricing since the service is fixed cost. Good vendors can discuss cost recovery with you and assist with billing to help fit your organization's business needs.