Sorry for the late reply. I asked about this, and it takes a bit of time to get response on those issues.

Plarium said that that the Prizes algorithm did not change.

Keep in mind two important things:

1. Whatever you think you know about the algorithm is only a guess made by us, players. There is very little that we actually know about Prizes, and those guesses are often completely or in part wrong.

2. You get some units for every finished Prize on which you lost some units. So, your "return" is not just the big win, but also those small wins.

Now, personally, as a fellow player, here is how I play Prizes: I send only useless units. Pirates, maybe Mercenaries when I have too many of them (compared to Fleet and Armada). Those are useless for normal fights, but I train them because I have too many resources. So, I send them to Prizes once or twice a year, and whatever I get back is welcome. If I got nothing back, I still wouldn't mind because - I repeat - I send only those unit that aren't really good for anything else.

As with all types of battles, don't send what you don't want to lose.