Design Versatility

This year I designed for some new platforms (iPhone, Symfony) that interested me. I considered whether I should learn to design on platforms which don’t interest me to diversify my skills or surprise myself.

I also considered whether it was smarter to market myself as a designer of WordPress-based sites, specifically, or a jack-of-all trades open to anything. I thought about what clients like to see in a portfolio vs. what I wanted to show.

One question I wonder each year is this:

Is it more attractive when designers can…

a) design like a chameleon in any style or genre appropriate to the project, or
b) design over a period of years in a consistent, signature style

What designers out there qualify for each of these categories? Which marry the two effectively? I’d love to know what others think, from the perspective of both fellow designers and people who have been in a client’s position.