Hackey
Those are two very different remotes. I am not an RTI user (I am not willing to give up the big customizable display on the Pronto, plus it is way out of my price range). But I think I might be able to explain the advantages of the RTI system to you.
Since he is adding sensors and the rest, I will assume that the IRF-6 is in the package
1) Assuming he programs all the commands through RF, when you press a button on your remote it will send a signal to the IRF-6. Since this signal is RF it can pass through any thing (walls, people, closed doors), the probability that the IRF-6 will not receive that signal is much more faint then IR. The IRF-6 can then be directly (wired) connected to the rest of the equipment (using CM 232 RS, or stick on IR emitters). This means that if you press the play button there is almost no chance that your equipment will not receive it. And if you have a macro (like the DVD on button you described) the possibility (more annoying) that just one of the commands is not received.
2) Sensors (Voltage or video) as there name states senses the state of your equipment. they plug into the IRF-6 and they tell it what to do. Let's say you were watching TV and decide to watch a DVD, your system needs to be smart enough to know that it should not turn of the TV, (that it just needs to turn on the DVD). When you press the button on the remote it sends a code to the IRF-6 giving it the order "use the sensors to see if the appropriate equipment is on, if it is not then turn them on". Some equipment have this intelligence built in (it is known as a discrete code) but others do not
----- A) A voltage sensor is used to determine if the equipment is on or off
----- B) A video sensor is used to determine if your system is using the appropriate input