LCD monitors are far better on your eyes since they do not have the flicker mentioned above. Another thing which I find in favor of LCD monitors is that many of them come integrated with a glare shield which enhances the viewing comfort significantly. Glare is responsible for some nasty headaches, so definitely get a monitor that has this as a built in feature.
As far as distance is concerned, I would say you should believe your own "eyes". In the good ole days there was a concern about sitting too close to the monitor since CRTs are a radiation source. Modern LCD monitors do not emit the same kind of emissions and therefore are much preferred over the old technology. Since there is no danger of radiation exposure you can pretty much sit any distance that is comfortable. The distance will be slightly different for everyone, so there is no right or wrong answer here.
As for a brand recommendation. You can never go wrong with Sony.
