User blog comment:Arbington/Platinum/@comment-3325589-20120718063846

Me and a pickup group made it to wave 9 on Firebase White against geth. Cerberus showed up on wave 3, and reapers on wave 6. I didn't find enemy numbers to be that much higher than on gold, and damage counts were higher but not overwhelmingly. Health seems to be what jumps the most: even mid-level units like geth pyros and ravagers took a whole lot of fire to kill. On other difficulties (even gold with the right setup and good players/characters), the group can kill enemies quickly enough to keep a chain of them coming from the spawn points, rather than all of them hitting you at once. On platinum you will get dogpiled, and you will play lots of revive tag.

On the other hand, the credits are pretty impressive. I got around 60-65k for getting through wave 6, compared to 75k for beating wave 10 on gold. To judge by the YouTube clip posted below, that means somewhere in the 130-140k range total. Still, if you're looking to farm money, and aren't in the uppermost tier of players, I think gold is your best bet: my loss on round nine took ~50 minutes (successful gold games take me 30-45), and would probably have run for more than an hour if we'd won. That's a lot of time, and your chances of success are a lot lower than on gold.