Alot of people still get this topic confused. The only time you need a large gate is if your trying to control really low boost like 6psi or less and your current gate isnt doing it or spiking. Think about it, to keep the turbo barely making boost you need to divert alot of exhaust away from it through the gate so the larger the gate needs to be to prevent a boost spike in the upper rpms as flow increases. The higher boost you run the smaller gate you need. If you running a turbo that can make a max of 20psi and you want to run 20 psi you dont even need a gate. The higher boost you run the smaller the gate can be and still divert enough exhaust away from the turbo. Displacement of the motor plays a large role in this as well. Alot of guys think they need to get a bigger wastegate when they are upping the boost, its actually the opposite. A small gate can handle larger boost better and really small boost on a big engine needs a big gate. Going bigger on the gate of course doesnt hurt either way, and when using a bigger gate with a boost controller it will be more responsive and stable when hitting peal boost.
There is a caveat to this, once peak boost is reached as rpm goes up flow goes up while the gate maintains desired boost. If the gate is to small to keep diverting the max cfm you will get a wavy boost curve or spike in the upper rpms. And again this has alot to do with size of the motor/cfm capability.