I'm not sure what the question is, but I'll try an answer anyway.
For large format, they provide lots of cool light. Fairly even. The new Aristo tube works well with the vc papers when using filters. They are small and light weight. They are diffuse, making for a nice low contrast light source. No Callier effect and dirt and scratches are reduced. On the bad side, the light output drifts with temperature and the 'thermo' doesn't work well enough to compensate. You will need a closed loop timer like a Metrolux. The two tube versions for vc printing don't put out enough light and exposures are excessive.
I use mine for 6x6 up to 8x10. It is a little slow for 6x6, but for everything else it is very good. For 8x10, very fast.
I used an Aristo on my old D2 for many years. I now use a diffuse light source on my Saunders. However after reading the material on the Durst USA site, I would strongly consider buying one of their condensor light enlargers if I were wanting to purchase the system that is best capable of producing fine enlarged prints.
I had never thought about it when I started that the thing that is nice about diffuse light sources is also a detriment as well. Diffuse light sources (cold cathode and dichroic) simply are incapable of producing as sharp an image as a well designed condensor light source. You will notice that I qualified that as "well designed". Not all condensor systems are equal.
I obviously have "no axe to grind" in this matter. This is my opinion based upon the results that I have seen.
I used condenser enlargers for years because here in Texas things used to move slowly. I learned to print on a condenser enlarger and learned to be a pretty good printer. For some reason and I don't remember why, I bought a coldlight and put it on my D2v Omega and I think I became a better printer right then. I currently have a closed loop system with that Metrolux II timer and the Aristo VCL 4500 head for the D2v. It has a blue and a green tube. It is everything I want in an enlarger light source and timer. So, to sum it up...Magic.
i have used a condensor light source since the early 1980s. it is in a durst m301. when i went to large format i bought a d3v and used that with condensors for the better part of 15 years. a few years ago bought an aristo cold light for it. i had always heard raves about how wonderful cold light is, and remembered when in college i used one for a little bit it worked pretty well. and thinking back, when i printed for a local portrait photographer, she had a diffusion enlarger so i jumped in head-first. to be honest - never really got used to printing with a cold light. the "smack you in the face" sharpness and contrast just wasn't there ( like what dnmilikan said ) so i put the condensors back into the enlarger.
call me crazy, but last year i bought an omega e4, and replaced the ailing omegalite with an aristo cold light source thinking that i would modernize it so i could use vc papers, and try it again. i found a set of 10" condensors "just in case ".
i too am undecided about what the raves are all about ...
I have an Omega E5 with the 5x7 version of the VCL 4500. Two color tubes for VC printing. Has two modes, one gives grades 0 to 5.0 with 50 settings. The other mode is split filter printing (Max green & Max blue).
This beast is awesome and the ability to dial in a 0.1 step contrast change is a real bonus. I get very manageable print times (sometimes I have to stop down a little more to give me more time if I have a complicated burning/dodging plan).
I also have an Omega D2 with condensor and a regular cold light head. Guess which one gets the most use!