I have a 3320 cab so i can give my honest thoughts.
I came from a 2520 see sig for info.
I was a little worried the 3320 was going to be really underpowered like everyone on here is saying.
After a year of mowing and pushing snow I have to say i am 100% happy with my purchase.
Does it have enough power to run the 72" deck? Yes. I have been able to mow through everything the 2520 could. the extra torque of the 3320 honestly made it not bog down as easy as the 2520 and this is with the aircon on.
For loader work and box blade work 3320 has more then enough power. Just put it in A range and it can spin all 4 all day long and loader lift capacity is the same as the more powerful turbo models.
The 72" blower you do feel the power drop and cant chug through it like you can with the turbo ones. (I've used a 4720 many many times so using that in comparison)
The biggest place the power is very lacking is C range going down the road. if i end up going up a hill on a soft dirt road the speed swing i've seen as much as 16mph top to 12mph on the climb.
Is the 3520 the better choice with the cab? Yes. Did i need the extra power? No. i'm 100% happy with the 3320 and have no interest in stepping up for what i do which is mow and a lot of loader and box blade work.
If i need raw power the John Deere 70 has lots of PTO HP to share