I have a feeling the Upgrade slots will come into play in ways that we dont know yet. Another thing to consider is... Don't trust the Ship Specs Page yet.
But According to the Specs Page -
The 325 would have better maneuverability but has less cargo space.
It has More Upgrade slots but possibly less of an engine/primary thruster
I believe the 325 to be more destruction based where as the Avenger seems to be more of a Disabler ship in its stock config but i could be wrong (due to the fact that it can be used as a bouty hunter/prisoner transport type ship.
As there has been Jack Shit written about all of the equipment listed, we really have no idea what to consider better.
But then there is also the descriptions of the ships...
Just because it's a rough galaxy doesn't mean you need to sacrifice your comfort: the 325a can come out on top in any dogfight. The 325a features and advance weapon payload as well as a custom targeting system designed especially for the 325a by WillsOp
The aegis Avenger has had a long and storied life as the standard patrol craft of the UEE Advocacy. Although aging, the Avenger features a sturdy, reliable hull and the capacity for larger than expected engine mounts and a front mounted cannon guarenteed to strike fear into your opponents.
If they hold true to the Descriptions.... This could mean a few things...
1. Avenger will have a better durability once shields are down
2. Avenger will have the ability to mount bigger/better engines.
3. 325a will have a better targeting system (unsure how they can pull this off)
4, 325a will a better payload (doubtful unless they make specific weapons that cant mount on the avenger)
Frankly, I like both ships but i like the sleekness of the 325 overall.
From a Idris Owners Standpoint... If you were to ask me which of these i would use other than Hornets in my Flight deck...
I wouldn't turn my nose up at either.