I don't have the experience of most folks here but I did switch fairly recently from a condensor (D5XL) to a diffusion head (DeVere 504). FWIW, here is my two cents (or is that here ARE my two cents?).
I had read that diffusion heads are more forgiving of dust and scratches (up to a point) and that you have more subtle control over contrast. My experience so far has confirmed this. It is also easier to use in that you don't have to swap filters to change contrast, you just adjust the dials. I really like this.
Having said that, it was very difficult for me to get used to the dichroic head. When you change filters in a condensor enlarger, you don't change the time (except when you change from the lower range to the higher range, usually at around grade 3). I found out the hard way that when you change contrast, the printing time can change a lot, and you have to test all over again unless you calibrate the head. This can be a very tedious process and, to be honest, I got through it only because I have a friend who was smarter than I am and whose capacity for technical knowledge is much greater than mine.
Furthermore, at first, it looks like you can vary the contrast from one end of the range to the other but in practise, it depends on the paper. I am calibrated for Ilford MG IV FB right now and if I started to use another paper, I would have to calibrate for it. I know how to do that now and it would only take a half day but the first time around, it was excruciating.
If you are a lot more technically oriented than I, you will have no trouble and I can certainly recommend some good resources, but it is definitely not intuitive. It IS really worth it and I know a hell of a lot more about paper and curves than I ever did, but be prepared.
