Sorry but I tried that Old Bay seasoning here in Colorado because I couldn't find Zatarains a few years ago to boil shrimp. Now the Coloradoans stepped up and you can get Zatarains.
Personally the Old Bay does not compare with the Zatarains for the Cajun boiled shrimp taste. That Old Bay is a Yankee thing. Ha! Ha!
Of course I've never had steamed shrimp. I always boil em! Send me a couple of yours’ steamed. I'll be able to make a decision just after two shrimp. The size doesn't matter. Bigger does not taste better. Case in point. All you can get in Colorado is giant King Crab. I don’t throw them in the garbage. I will eat them. But if you had them sitting next to the New Orleans Lake Pnchartrain crabs, I’d let you have the King Crab. I’d have to work harder with the Ponchatrain crabs to peel them but to me it would be worth it. I can peel Shrimp and or Crawfish faster than you can say PRS3000. As a matter of fact I can peel em faster than you can say Yamaha. Ha! Ha!
No offense friend!