FX FX Panthera Compact Hunter .30 vs. BRK Ghost HP .30 Cal.... Which is better and why?

Different animals! You're comparing a bullpup with a 580mm barrel and a 480cc bottle to a compact rifle with a 400mm barrel and a 300cc bottle.

A better comparison would be the BRK Ghost to the FX Impact, or the BRK Pathfinder to the FX Panthera Compact Hunter ;)
In my Panthera Compact .25 Cal I have two bottles, the small 300 cc in the rear and a 580 cc in the front.

If I would buy the Ghost in .30 Cal it would have a 700 cc bottle and if the Panthera it would have the two bottles, as my .25 does.
 
In my Panthera Compact .25 Cal I have two bottles, the small 300 cc in the rear and a 580 cc in the front.

If I would buy the Ghost in .30 Cal it would have a 700 cc bottle and if the Panthera it would have the two bottles, as my .25 does.
Given this information, the major difference would still be the difference in barrel lengths (580mm vs 400mm). It will take a lot more effort to push the same projectile the same speed out of the shorter barrel.
 
Wish I had both or either as to provide better input. But gun layout plays a big role in my purchases. As does overall weight. Use case will determine what is best. Sometimes it is just preference. Bullpups are generally less ideal for off hand shooting. They tend to have some other proclivities as well depending on the model and design. Overall, though, the ghost appears to be of a more robust design, so that is a valid consideration as well. I'd dig deeper and search/read more topics about each platform. I don't trust you tubers so much unless they are purchasing the guns with their own money.
 
Bullpups are generally less ideal for off hand shooting

I am able to shoot my ghost better offhand than my red wolf. The wolf is just a bit more barrel heavy. I agree with the barrel length difference too that gives the ghost a big advantage in my book. Then there’s always the soda straw vs solid barrel. I’ve slid my ghosts bottle off my styx so many times with the barrel landing on the styx that I don’t even give it a thought anymore as the shot goes where it’s supposed to.
 
In my Panthera Compact .25 Cal I have two bottles, the small 300 cc in the rear and a 580 cc in the front.

If I would buy the Ghost in .30 Cal it would have a 700 cc bottle and if the Panthera it would have the two bottles, as my .25 does.
No clearance issues with your 580 bottle & moderator on the compact hunter ?