I am going to tell you what I do, first off, I don't find printing at home to be cheaper, but it is just me.
I use shutterfly for all my printing...and here's why, first off and the biggest reason, shutterfly prints the date the picture was TAKEN on the back of your prints. Snapfish will print the date the day your pictures are printed!! BIG difference!!!!
The prices are comparable to other sites, and I look for coupons and print when I get them.
Also, shutterfly will tell you when a picture is going to get distorted when you blow it up. That helps a lot to prevent pictures from being useless!!!
If there is a picture, and it tell you it can't be big at all, not even 4x6- you can generally print in wallet size, you will get 4 of them but at least you don't lose the picture!! I have done this for some pics that I got off the internet for a project!!