Believe it or not I actually use both...If your like me I almost always need my phone and only sometimes need my wallet. Why carry both when you can ditch the wallet for daily use and keep the case? 

Wallet Phone Case:

• I only use at most two different credit cards on a daily basis.  I put my favorite MasterCard cash back card on top with my Venmo Visa just underneath in case I am at Costco or someplace else that needs a Visa.  
• I keep my drivers license on the on the bottom so I have it whenever I have my phone with me (which is almost always) 
• With only 3 cards in the case its super easy to access any of the cards, and when I travel I often put my room key card on the top for convenience.

Slim Wallet:

• I store all my other credit cards and medical cards in my slim wallet
• Anytime I travel someplace where I may need more than my drivers license and a few credit cards I bring my slim wallet with me in my backpack or luggage.

I use my wallet cell phone case as my everyday wallet and I know anytime I have my cell phone with me I have everything I need.  No more forgetting my wallet!