Take what i say with a pound of salt, as Ive pretty much just been using 10% of my paycheck to buy all the apex and "!!" via $10 sales, but in my experience Pacific Wasteland seems to be better for grinding. While it gives a moderately reduces payout compared to Arctic Apocalypse, I've tried both maps with pretty much every apex and some of the "!!" sharks i own and PW feels a lot more reliably survivable, it could just be a skill issue on my part, but I prefer to grind with my favorite sharks, and a majority of my favorites demanded a lot of focus to actually survive Arctic Apocalypse with any semblance of ease (id like to clarify that my favorite sharks are NOT the best though, like Veteran Great White, Apex Megalodon, and Mecha Sharkjira without stat upgrades or the ultimate ability unlocked)