Hey Ash. I have one xr30w Pro g4 mounted 12 inches above the water over a 36" tank and I get a good amount of light anywhere I want it. I grow sps on the top rocks very well and havent had problems with anything else. However, on a 36 inch tank, you will get some shadowing depending on how your rock structure is formed.
Here is a rough idea of the PAR I am getting. Keep in mind this is only at 70% intensity and I have since been raising incrementally to have more light available for the corals who need it. You can get away with one having a similar setup as mine, but in reality if your rock structure is not tapered off as shown in the sketch, you will have a hard time growing SPS in other spots than the middle. Having a shallow tank (40g breeder @16" depth) is also helpful as I can raise the light up higher and still get good penetration.
Now back to your question.... I personally have only used the g4 pro and cannot really speak for the non-pro version. The pro offers phenomenal colors and like all radions, has an excellent user interface to work with. It would also be worth looking into getting 2 radion xr15 pro's and you will get less shadowing and would be better for a more pillar like design. I would recommend going with the pro version for the little extra PAR boost (no evidence to back up but generally more LED's=more PAR).
People may disagree, but eBay has an abundance of radion's for really good prices. People are always coming in and out of the hobby and there are a ton of deals in other places than the retail stores. Just be patient and a deal will eventually come.
Best of luck.