I've read good reviews on both the DS and ETX series. Your website is very helpful. The DS-EC models do not include the Autostar whereas the AT models do. Having the Autostar GOTO computer will help you locate objects that you might otherwise never observe, however, you'll need really dark skies to effectively use a 70mm aperture telescope. This measurement refers to the diameter of the eyepiece tube, and hence what size eyepiece will fit the telescope.
Some telescopes use different size eyepieces.
There are adapters to match the eyepiece to the telescope if you can't or don't have a match. Track, point, chase satellites, etc. Due to the mount geometry, they have different travel limits, but that's not much of a factor. I have just finished a new DS powered mount for my Astro Rubinar. Works great and very portable.