I find HSV easier for certain effects, and RGB for others. If you are happy with RGB no need to convert, especially now that rgb() supports all the extras as hsv(), such as HDR support where possible.
However, learning HSV may open up new ways of doing things. Of course if you have interesting textures in an existing pattern, feeding them to hsv() can produce interesting results!
I like to think of hue as a color wheel, values fed in to the first parameter go around the wheel, picking different colors. Imagine this:
Positive values go clockwise, and negative values go counterclockwise. If you give hue values more than ± 1, it just “wraps” around. I find this very handy for some kinds of patterns.
Saturation lets you switch it up from color to pastel to white. And value is basically brightness. When you combine it all, you get something like this (though they reversed the hue direction, it still goes from red to orange, etc)):
