I did my first summer internship at Eckerds/CVS and my second internship at Walgreens. I wanted to see operations at both the major chains and compare them.
Walgreens has a true internship program with corporate meetings, projects to work on, as well as normal tech work. This program has been around for a while. CVS told me during a career fair that they are going to start a true internship program this year. Before that, they just threw you to the wolves.
Doing the actual tech work was the same between both chains. They both had high volume, drive throughs, screaming customers, etc.
When you become a pharmacist, they are a little different. Walgreens has 8 hour days, so you'll be working 5 days per week. CVS has 10 hour days, so you work 4 days per week and it's easier to pick up extra work. CVS will also place you at a store immediately upon graduation. Walgreens makes you be a floater for 6 months first.
Both companies do 401K matching, but Walgreens has a better stock option plan. You get employee discounts at both stores, which helps on things like toothpaste, deoderant, etc. Those little things add up.
Both companies offer tuition assistance, but CVS gives you more money. It was 5K per year last time I checked. I didn't do this, because I wasn't ready to lock myself into a company.