What are the pros and cons of writing nozzle size vs using e3d style dots on nozzle?
dots
First of all, reading the dot pattern: for all but the 0.15, the total number of dots is read, and there is only 1 dot per side. So a .5 nozzle has dimples on all sides. The only outlier where the dots are not all one next to another is 0.15, which has 2 dots but they are interspaced by one blank side.

0.25
0.3
0.35
0.4
0.6
0.8
0.5 (which was added after the .6 and .8 had already been established)


2 interspaced ones - 0.15, also added after the 0 to 5-dot group had been established.

dots vs. inscription
The inscription is, compared to the dot pattern, much more shallow and can vanish under scratches. Also, the dots are easier to recover from being caked in plastic.
On the flipside, the dot pattern isn't easy to read intuitively, it doesn't follow an easy pattern (the 6 and 2-interspaced-dots are later additions into the setup).