Here is my thinking regarding the Avanti AstroPlane, compared to what I call the Coppers Top One antenna. See Manual for the Sirio New Top One image below.
IMO, the original Top One antenna was a knockoff of the Avanti AstroPlane. Maybe CTE stopper production of their Top One or went out of business. Maybe Coppers stopped selling the Top One.
So, I refer to this old CTE antenna as the Old Top One and it was sold by Coppers Electronics.
I recall Coppers sold the Top One and it was possibly a bit larger than the Original Avanti AstroPlane. As time went by Coppers either quit selling the Top One or CTE stopped producing the Top One.
Closer in time to todays Sirio New Top One see image below) makes their version of the Old Top One, The New Top One uses a gamma match to help tuning-range and with several radials possibly adding a bit more bandwidth at or below 2:00:1 SWR
The names and descriptions of this antenna design is of little value to the comparisons of these antennas in actual use. They seem to me to all work about the same or similar...and do a very good job with your radio receive and low noise levels,,,and with transmit...producing a very robust RF pattern at low angles at the Earth's horizon.
I also posted the Eznec models for the Sirio M400 and the Siro New Top one below to compare the possible advantages of these 1/2 wave antennas...
regardless of how described or named.
I also posted some other the RF patterns for several other antenna at 1/2 and 5/8 wavelengths for some added comparisons of the RF patterns, gain, and angles.