I just returned from the "local" (cologne) guitarshop and I tested the Jackson RR24 and the Ibanez Xiphos. The Amp was a Powerball with an ENGL Vintage box (Because that's the equipment I have).
The Jackson RR24:
First of all: I can't understand why some people always bash this guitar. It is great, particularly because it's 1090 Euro.
The Sound is warm and the harmonics come easy.
Playability was cool, but don't await a wizard neck. It's a bit fatter than Ibanez Wizard necks, but I learned e-guitar on the strat of my father, so that was no problem. Some people whined because the access to the higher frets would be not so good. Well, I don't know how it is when you have short stubby fingers. I have "piano-fingers" and I had absolutely no problem.
The workmanship is ok. The paint jobs especially at the bevels could be better.
The Xiphos:
770 Euro (ca.) is a strong argument! It sounds great and agressive, I never expected something like this from Dimarzio, typical brand for guitar heroes.
Workmanship is good, but to achieve a better playability, you'll definitely have to set it up by yourself (or someone who does it for you). Plus, they put on .009 strings on the guitar, that SUCKS. Especially when you want to bend strings, you feel like playing spider webs. I played a 1 1/2 tone bend and the tone was far from being good.
In the end, it's all about personal preference. I like the tone of the jackson, I just can describe it with the word "sweet". And I like it's look much better than the xiphos (cool shape, but the sparkling red is weird).
Plus, they have different concepts: The Jackson has just 1 Pickup(EMG 81), the Xiphos has 2.
As I said, I would take the Jackson, but I have to admit: The price/value proportion of the xiphos is better.