If you have a 4 foot cage, get a 80 watt RHP. Both Pro products and RBI are identical in how they operate, how long they will last, and how safe they are. Bob from pro products will ask questions about your setup and house to determine the size. He has a ton of size options. RBI has preset sizes and as one who has one in the 4 foot cage I have, the 80 watt is perfect.
If you do not want all the fancy visual LCD and safety rely bells and whistles, get he herpstat EZ line. It offers the same proportional heating just without a LCD screen to display the temp.
The RHPs are the simplest things to install. A few screws and you are all set. RBI RHPs come with a snap in plug so you can run the power cord through a hole and I beleive Pro products are the same. Put the cord toward the back, the RHP facing the right direction and don't install it directly against the wall. That's it. If you can screw in a screw into a wall, you can put in a RHP.