The Reilly set up is a similar design of the GM A body layout, which means it has all the benefits and drawbacks of those systems.
XV is a three link design which is much more popular with the road racing crowd for its ability to articular without binding.
My perceptions of these systems;
The benefit people are seeing with these systems is having someone else spec out all the wheel rates neceessary to balance out the car, thus achieve excellent handling. With the proper application of formulas, the same results can be produced with the OEM suspensions, but most people do not how to get there, of ir they have hte books, have not bothered to do all the calculations (they can get extensive). Tires only care about the force acting on them, not the system appling the force.
Coil overs are nice in that they are lightweight, quickly adjustable, and have a plethora of available springs rates. All great things in a competition environment that require quick, minut changes to adjust the car. For street applications, most drivers will never bother to change rates or perform the adjustments that make coil overs the prefered method of suspending a competition vehicle.
They do look freaking cool though!!
It all comes down to personal preference, application, and budget. There is no wrong or right answer to any of them.