I don't know how one would test it, but for me at least reading an analogue clock seems a simpler process than a digital one, because the information doesn't have to go through the verbal centres of my brain. For the record I'm in my early thirties and learned how to read digital clocks before analogue.
My impression from the comments in general is that different people represent time in their heads differently; it seems that the way you do it is closer to the way that's displayed on an analogue clock, so digital requires translation, whereas for some other commenters it's the other way around. Hmmm.
I was thinking about this phenomenon today. Digital clocks are so common now that I don't often need to read an analog one, much less in a hurry. I worry that I'm losing the ability to do so. (The worry is a little bit because I might still need it at some point, and much more because being able to quickly read analog clocks makes me feel like a grown-up.) In particular, when I am called upon to read one, I'm embarrassed by how long it takes me to do so. It's only several seconds, but that's enough to make it clear to anyone watching that I had to stop and think about it.
But then I caught myself, and thought, wait a moment. Am I actually much slower at this than I used to be? Or is reading an analog clock really just a noticeably slower action than reading a digital one? This is intuitively plausible; it has more mental steps. Rather than comparing my current analog-clock-reading speed with a previous one (which I don't really remember), I'm comparing it to my digital-clock-reading speed, which doesn't make sense. I was going to ask how you'd design an experiment to test this. Then I remembered that not everyone is young enough to have to speculate about what it's like not having mostly digital clocks around. :P So if you're old enough to have significantly more practice reading analog clocks than digital, how long does it take you to read one? Is it noticeably longer than reading a digital clock? If you aren't, and have a significantly different experience from mine, I'm interested in that too.