The 9452 is 0.04 quicker (0.11@6v)... but you really don't need all that torque.
here are the specs on the 821s:
Type - Digital Hi-Torque
Torque:72 oz/in @ 4.8v, 88 oz/in @6v
Speed:.19 sec/60° @ 4.8v, .15 sec/60° @ 6v
88 oz/in is plenty for the Hurricane. Even the 72 oz/in @5v... is enough. The heli only weights 2200 to 2500 grams... depending on the batteries you are using.
Speaking of batts... it kinda sucks on anything less than 2500s... and I personaly use 6S 3200s on up to 3800s (I also have a 5S 5000 & 2 FP Evolite 4150s that I like to fly in it).
Also... the stock kit motor also sucks. For sport flying and mild 3D... the Z20 980kv motor is real easy on batteries. For hard 3D... I would get a scorpion 3026... or a Z30. I have a RCP 1500w 1100kv now... and it is a rocketship with it... but I only get 7-8 min on 3200s (which really is not to bad).
For less than one 9452... you can get a new set of 4 -821s here in the RR classifieds. They go from $60 to $75 a set.
On the plus side - I Love flying this heli. I have a T450 & a T600n... and the Hurri is my favorite right now. It is a great size... light... highly configurable, lots of bling and upgrades available... and spares are cheap (which is a good thing for me).