Both products work the same, you fill out a questionnaire so they can decide what products you might enjoy and then they put together a package and ship it out. With Ipsy, they always send your products in a cute little cosmetic bag and I use those bags for various things around my house that don't usually have anything to do with cosmetics. With Birchbox, you don't get the cute bag, but you get to pick one of the samples you get each month and still get to be surprised by the rest.
The problem I had with both services is that I might get the same product in a different shade or the same shade of something in a different brand in back to back months. I don't need 2 lipsticks in a pretty berry shade, even if they are different brands. When this started happening with Ipsy, I switched to Birchbox, but it happened with that product, too. The positive thing about these products is the price. Each box it $10 and you will usually get a full sized product as well as a few sample sizes. These services would be great for someone who is starting a beauty routine or trying to shake up an existing rut. As for me, I have a ton of makeup and hair products that I've purchased over the years that are cluttering up my makeup bag as it is.
Did you have a different experience with these products? I'd love to hear about it!