No, the non-XL Define has just had more revisions as I think it's been out longer. The XL R2 is as up to date as the R4 in terms of features I believe.
The 500r is very nice too, although not sound insulated which was a must have for me.
So these 1440P monitors I keep hearing about, I understand apart from one available on eBay the majority of the decent makes such as the Dell or Asus etc don't do 120hz.
So my question for those in the know, as I mostly play FPS games would I be better sticking with my current 24" 120hz 1920x1080 monitor or going for a 27" 60hz 1440P monitor?
I remember going up to 120hz from my old 60hz 1080p monitor was a huge difference and everything felt so much smoother.
1440 will look superior in every aspect. That said i have never been able to get used to FPS games at 1440p. I always find myself going back to 120hz if I'm having a COD or BF3 session.