Here are the + and - of each, based on my test observations:
Maple leaf:
+lower price
+higher velocity, you can feel when your hit
+realistic
-only shoots in a arc
-BBs that face toward ground are ineffective.
-Easy to loose spoon and pin (but you can get replacements at Army surplus stores)
Tornado:
+better BB coverage on target
-Cost
-lower velocity, hard to feel the hits sometimes
-not very realistic
The other thing about Airsoft Grenades, is you have to be mindful of throwing and recovery. Some people paint parts of them blaze orange so they are easy to find in heavier brush.