(versus fussing with the filters)
VC filters are much easier and faster to change out than dialing filtration with a dichroic head. Have experience with both, dumped all my enlargers with color heads. The filters will fade with either, filters are ridiculous to change with dichro heads, new pack of VC filters fixes the other.
You have a point with regard to instant single or half grade filtration changes, but when one requires a very subtle change, say, maybe a ¼ of a grade change, this requires a head, either a colour or dedicated B&W VC head. Little things like this are a very nice bonus. I actually have filtration values stuck on my darkroom wall that gives me 1/8 of a grade difference. When one is in the groove printing a high key print, then really small grade changes, often coupled with a 1/8 or 1/10 of a stop density change, can often turn a very good print into an unbelievable print that a client goes ga ga over. Split grade printing is very good, but the miniscule changes available with a Dichroic head anywhere along the gradation curve possibilities of the paper, really give one great control.
As for dichroic filters fading in a colour head, maybe, but so far I have not witnessed this. My own colour enlarger is a 1981 build DeVere 504 with a Dichroic Colour Head. It was installed in a colour lab in Melbourne in very January 1982 during the summer break. From that then on it worked two shifts each working day starting around 0800H and finishing up around 2130H each and every day until it was sold and purchased by myself in January 2001. In short, I know the life of my enlarger quite well. The filtration hasn't shifted enough to be noticeable since I purchased it from my old work place almost 16 years ago, it still works very well 35 years later still using the original Dichroic filters. They have done a shed load of work, as are the Dichroic filters in two other DeVere 504 enlargers from my old work, which now located in private darkrooms and still pumping along.
I have used an assortment of colour enlargers in an industrial setting, I have never heard of one having its Dichroic filters changed. Dichroic filters do fade, but as far as I understand, not enough to be changed when used in an enlarging head for photographic purposes.
Mick.