The difference is that one method is destructive editing and the other is non-destructive.
If you select 'Open Copy in Audio Editor', a copy of that audio event is created (and added to the folder containing the original audio event, it's name appended to show that it's a copy), and that copy audio event replaces the original on Vegas Pro's timeline. Any editing you do in the audio editor therefore only affects the 'copy' - and the original audio event is retained in the project folder if you want to go back to the original at a later time.
If 'Open in Audio Editor' is selected, then all the edits made in the audio editor affect the original audio event on Vegas Pro's timeline. This is effectively a destructive editing approach unless the audio editor has the ability to save all the editing as a project file like in RX. Also, destructive editing with the 'Open in Audio Editor' option can be avoided if in the audio editor, saving the edit as 'Save As' is chosen and a newly named audio event is manually created (i.e. the save is not made back to the audio event on Vegas Pro's timeline). But that will then that will mean that the newly created edited audio event will need to be swapped manually in VP.
@Dexcon - Thanks for the speedy response! O..K… And yes this is me in iZoRX. Sooo…. As a “COPY” I get a reassuring TAKE1 back in VP. If I just “OPEN” I wouldn’t get a “reassuring” TAKE1 back in VP?
Besides personal choice, I can't think of a reason why the original audio track would not want to be kept "just in case". But I suppose that we all keep a backup of media on another drive anyway for that "just in case" moment.
I must admit that I use a rather convoluted process with this because mostly I go to the OPEN option to go to Sound Forge Pro and then via its Tools menu selection to go to SpectraLayers Pro. The obvious question is why not use SpectraLayers Pro as the preferred audio editor. The reason is that when SLP is selected as the preferred audio editor, the entire audio event opens in SLP when I only want to deal with a limited length of that audio event. Whereas when Sound Forge Pro is selected as the preferred audio editor, the entire length of the audio event also opens, but the section of that event as is edited on VP's timeline is highlighted in SFP. That highlighted section is the only section that opens in SpectraLayers Pro when SLP is accessed via SFP. After editing in SLP, the edit is saved from SLP with the appended name created by SLP and saved to its own folder. In VP, the audio events have to be manually swapped - and because I exit Sound Forge Pro without saving, the original audio event remains unaltered.
🎬 ... Roll ... Speed ... Action ... Cut ... Gate Check. What a great industry to be involved in - past or present - either professionally or as a personal pursuit.
Since you use the Open Photo Editor tool in HOS, try the Open Audio Editor tool as suggested by @walter-i. which works the same way. The take is added "after" editing--not before--which has always been a perennial problem with Vegas. Plus it avoids having to delete a take if you decide that you don't want the changes.