well the rsx3.5 and viper 791xv should look the same since they exactly the same. The only "real" clifford stuff is the stuff with G5 technology ie.the avantgaurd5. Since you are talking 2-way you prolly aren't interested in this. As for Valet which is this year's hornet two way it differs alot from the viper and and clifford. The brain is differen't also the features are pretty cool but the range is so so and the delay time between car and remote is kinda slow.
If you are looking for more distance check out compustar.