It's been interesting to notice how time spent doing caricatures is affected by the format - especially when the formats are similar. For instance, the above pic of Billy Bob took me: 2h 20m. I found that on average I would only spend an hour to 1h 30m on real pencil drawings - for a similar overall effect. The only theory I have is that with the digital pencil I'm probably editing and trying different things along the way - sometimes scrubbing out whole sections of an involved piece. With real pencil I'm committed - but I do a lot of screwing up of paper.