My futures trading is split 80% NQ to 20% ES, reason being that (in my opinion) there are better (cleaner) moves and signals in the NQ. I don't have specific evidence that points to that conclusion - it is just my "feel" after looking at futures charts for about a year.
But if I trade after-hours, I always trade the ES (that is where I get most of the 20% referenced above). The reason is simple - the ES is more liquid than the NQ, and you can get in and out with less slippage.
Even though I focus on the NQ, I always have the ES chart up. I often see either the ES or NQ hit a level and react whereas I would not expect a reaction just looking at one of the charts in isolation.
Yesterday was a good example. The NQ broke the previous day's low, but reversed on the way to the Fibonacci extension (FE). The logical target was the FE, and there didn't seem to be anything to stop price from reaching that point. However, if you look at the ES chart, you will see that it hit its FE, reversed, and was headed back up; in this case, the strength in the ES was lifting the NQ. If you had both charts up, you would have been watching that level in the ES and you could have still exited the NQ with a nice profit (notice how the NQ also printed nice "offsetting bars" at that level).
Check back over the weekend as I hope to post some thoughts on plotting Fibonacci lines.