Sounds like you are talking about clean speed or green dot. If you look on the flight deck of the bus you will see an expedite button on the FCU, pushing it will let you climb at green dot and give you max climb thrust within 1 second, nearly all operators have it taped over or removed because it can get you into trouble at high altitude.

I dont know anything about how airbusses work.

But no, you would not want to reduce too far back cause yes you could get into trouble then.

I used all modes today. Started in VNAV as we were on profile. Then after an intermediate level off we were high so LVL change to get down and then used V/S with the RoD in the FMC descent page as a guide while being vectored for the approach. Then back into VNAV for the GPS approach. 

 

The mode I use depends on the situation. VNAV is great. Good protections and profile management. However, it will need to be updated with any new speed restrictions given by ATC. A 310kts decent is different to one at 250kts. VNAV is great when given an early decent. 1000fpm until it catches the profile. VNAV is not a good mode to use if you are already high. Best to use LVL change. If you used VNAV it normally pitches down and gives you a crazy RoD as it attempts to catch the profile. The airspeed shoots up until it hits the VNAV limits and then transitions into VNAV SPD. It's a wild ride and not fun close to the ground. 

 

In a climb I will not use V/S up high above FL200. Its a bad way to end up stalled. Normally use V/S on the climb if the change in altitude is 2000ft or less to keep things smooth. 

"I used all modes today"

 

Yep, that sounds like a typical day.

 

You see what I mean?
You are talking performance over a longer time.
I was talking about a short climb/descend performance boost.

 

Gotcha - thanks for the clarification.  I see what you're getting at now.

Yes, so with V/S you are doing it the difficult way.

 

The CDU descent now feature and pressing the Altitude selector give the exact same result.

The only difference is that the CDU Descent Now feature always works, but the Altitude Selector only has the same effect when pressed within 50nm of the Top of Descent symbol on the ND.

Further than 50nm from the Top of Descent symbol, pressing the Altitude Selector, starts a Step Descent that will not intercept the Vnav Descent Path.