The website told me "e series", "600 series", "i series", "s series", "900 series" - then even though they are called "series", most of them have only one product in them.
I wanted something mid-range to get started and the product picker tool they have recommended me the e5 because I have a pet. I went through dozens of reviews to finally learn that it doesn't have a camera and vSlam, so it just slams into everything and doesn't map my place over time.
I went with the next higher model that has a camera, the 960 and it has been doing a good job. As a techie I was a bit disappointed that I picked a model from 2016 and that they kept the smarter features like keep-out zones for the higher ones. Eventually returned it and got an i7 for a similar price and it's a pretty fantastic product, though I ended up paying much more for my experiment than I anticipated...
The product comparison page ([0]) is doing an ok job but I wish they'd make product selection a bit easier.