The electoral system has been around a long time and is, at least, predictable. A constitutional convention would not be. Many of the players would be completely different. There are really no rules for one. There would be too much opportunity for those with sinister motives to have undue influence over it
I may be wrong. I have been before but not very often.
The players in both cases are the same. The players are the state legislatures.
When so many states have stood up to Obama over Obamacare, illegal alien invasion, and various executive agency diktats, it is a shame they are not given a lot more respect.
The states are our last line of defense. We must use them.