I usually do Walgreens because it is fast and they always have a coupon. I have done Shutterfly but now they offer to send them to Walgreens too so I guess its a win win!
I print my own with my selphy. Occasionally I'll use the app on my phone "Free Prints" when I want several pictures and I'm not worried about resizing, etc. It's 85 prints per month free, and you pay shipping (usually $10).