There are really only two choices, the Pro-HD or the SOLO. There are two main differences, price and the ability to watch a different channel than what someone is watching on your tv. I bought the SOLO and am happy with it except for the times I am not able to watch what I want because my wife is watching tv in the family room. The Pro-HD has a built-in tv tuner that allows you to watch a different channel.
With your Slingbox, you can watch tv on your computer, laptop, or some smartphones (require an additional $30 app). The SlingCatcher is no longer sold. It was a device that could receive your Sling tv signal and send it to a different tv.