On the verge of vs. About to

Is there really any difference between about to and on the verge of ?

This is the kind of question which if you ask natives you maybe sometimes get different answers.
Everybody has their own opinion and instinct according to his experiences in facing and using the expressions.I think this is probably because these two idioms have a wide usage in both written and spoken English that hardly may everyone take notice it.
What follows is a summary of different point of views on the distinction and the usage of the two idioms .
As a non speaker of English ,however,I think the article may not be free from any
mistakes and I would appreciate it if you inform me by your comments.
Both expressions mean very close to happening ,but there are some shadow of differences between them:

1-On the verge of is commonly found in literary and formal language and suggests a dramatic or momentous concept:

-I'm on the verge of a nervous breakdown /suicide/getting married
-The country is on the verge of a revolution /a big breakthrough/ a social upheaval

About to is neutral and mostly turns up in slang ,colloquial ,informal and nearly formal contexts which include either important or unimportant circumstances.
In addition to that it can replace with on the verge of in the above examples,it would be used in occasions which signify an unimportant and trivial step:

-I'm about to call my mother .
-Paul is about to having lunch.
-My mother is about to go to sleep.
-She's about to leave the house.
-My father is about to switch off the lights.

In the above contexts "about to" is preferred over "on the verge of" because they don't convey momentous circumstances.

2-The other distinction is that the sentences with "on the verge of " are thought to sound as though you're being pushed to do something by your surroundings or something in the situation while "about to" tends more towards focuses on the "next step OR the next thing you are going to do:

-I am on the verge of leaving the house= I have to leave the house for example because I must go to the work.
-I am about to leave the house= I will leave very soon.

3- Some people believe that the former one is found in negative contexts and used when you are getting close to doing something unwillingly:

-The country is on the verge of a crisis.
-He is on the verge of a serious illness.
-They are on the verge of fighting.

4-"About to" tends more towards focuses on the "next step OR the next thing you are going to do;whereas "on the verge of" tends towards "significance".

-I'm about to go into town, do you want me to bring you anything?"
-I'm about to eat dinner, can I call you back later.

In brief," about to" has a wider usage than" on the verge of "and it can turn up nearly in all contexts ,whereas the latter is found in dramatic ,formal,literary contexts.