Pros of using pen:
1. faster (no noodling or erasing)
2. more confident sketches
3. it looks cool
1. can't erase! (which force you to learn to be more confident)
*yep, only one con!!!
This is the first week exercise from Dynamic Sketching -- learning how to create texture. The idea is to create value from 100 to 0 (black to white). Do as many different texture as you like. It does take a lot time at first. And like all basic things, it can be tideous but very important to learn.
ps. I use Sharpie Ultra Fine Point permanent marker. I like how the ink flow. It's also very cheap. Double win!