Are you suggesting setting these database settings whenever you connect to the database? That's not necessary. You should set this when the database is created, and only use those that you actually need. From your brief description of your business case it would seem that you need both, but I think READ_COMMITTED_SNAPSHOT could be enough. Perhaps you should provide more information regarding the actual business needs (in business terms).

As far as the differences between SNAPSHOT and READ COMMITTED SNAPSHOT are concerned, perhaps an example might help:

http://milambda.blogspot.com/2006/09/snapshot-transaction-isolation.html

(Skip to Mental Aggregation if you're only interested in the differences.)