I prefer to use excel as a tool to work with because you have instant visual feedback on backtesting and complex formula manipulation where you need to see each portion of a process broken down.
Also, using excel allows easy importing into MSAccess for those things that just can't be done without some SQL power above and beyond the limited query abilities of excel. MSAccess also exports quite cleanly to excel.
I would strongly suggest using Excel as your primary storage and manipulation tool, and save the bigger guns of MSAccess only when there is no reasonable excel option.
If you do go right into MS Access, make sure you have a firm grasp on the basics of RDBMS design (primary keys, dependencies, data types) because one little error in the setup phase can go unnoticed for quite some time, rendering practically useless data... the same data that a quick eye and/or conditional formatting would have made obvious in excel right away.
for example, a simple =countif() function in excel will show you the most popular number in a column (or array), but if you want the top 5... nothing beats the Access 'SELECT FROM' query with the 'TOP 5' modifier set.