Aristo, the main US manufacturer of Cold Cathode light sources, was acquired by another company and ceased production of new heads. They still offer some replacement tubes, but they tend to be pricey. Most modern enlargers with diffuse light sources now use halogen bulbs with dichroic filtration for color or variable contrast.
I've owned Durst 35mm, LPL 4x5 and 5x7, and Beseler enlargers. They are all fine pieces of equipment. I also own a Zone VI 5x7 Version 2 enlarger with variable contrast cold light head.
1. I don't recommend the Zone VI for formats smaller than 4x5--you are wasting too much of the light illuminating the negative carrier and not the negative. For 35mm the light is dim and hard to compose the photo. For 4x5 it is oversized, in my opinion. For 5x7 it is one of the few moderately price systems, but available used only.
2. I like Durst equipment, but it depends on whether you can get the necessary accessories & parts.
3. LPL enlarger work very smoothly and they are very well crafted. They are my first choice for an enlarger with a diffuse light source.
4. The Beseler was a 6x7 version with the 23C support, no longer offered in that version. It was an excellent piece of equipment, but it was diffuse light source with color dichroic filters.
If you are looking for new equipment, it depends upon your local pricing. Be sure to price the negative carriers and lensboards.
As to a choice between diffusion light sources and condenser, it's your opinion that counts. Early on I used condensers, but now use diffusion and would prefer diffusion. Great prints can be made with either.