Lunivore
There are two models that you can only get as Capital Freighters in varying lengths; Sentinels (long ones shaped like a bread knife) and Venators (look like an Imperial star destroyer). These will not normally show up in a system without going through the freighter fight. (They did show up for me in the expedition which was weird but I haven’t seen them in normal play).
Other than looks though I think there is no difference, and the smaller non-capitals are much easier to get.
I settled for an A class. It’s plenty.
It was one with a message that someone copied from a commit I had made a full year before. It broke the build right before a release and the commit message bore no relation to the changes, of course.
Because they had copied my message, it had my initials in. I had visits from irate managers in other buildings who ranted at me for a good 5 minutes without letting me get a word in to tell them that 1) it wasn’t me, and 2) undoing a subversion commit was a one-line command and not a good reason for the stupid amount of drama (there were no database or other irrevocable changes).
The last manager to speak to me told me it was still my fault as it was a bad message in the first place. The message read “Fixing typo in the audit log”.
If I understand correctly, you have a better chance of an S-class freighter in Outlaw systems. The capital freighters can only be got from a freighter fight, which happens after at least 5 warps and at least 3 hours gameplay.
You can save before you do the fight and reload if the freighter isn’t S-class. Reports elsewhere suggested it still took hours to find one.
Note you can tell what class a freighter is by looking at a wall in analysis mode in the landing bay.
But an A-class is plenty good enough!