Taken from Wikipedia:
A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases regulates the turbine speed, which in turn regulates the rotating speed of the compressor. The primary function of the wastegate is to regulate the maximum boost pressure in turbocharger systems, to protect the engine and the turbocharger. One advantage of installing a remote mount wastegate to a free-float (or non-WG) turbo includes allowance for a smaller A/R turbine housing, resulting in less lag time before the turbo begins to spool and create boost.
External wastegates are commonly used for regulating boost levels more precisely than internal wastegates in high power applications, where high boost levels can be achieved.
Wastegate sizing is inversely proportional to the desired level of boost and is somewhat independent of the size or power of the engine. One vendor's guide for wastegate sizing is as follows:
big turbo/low boost = bigger wastegate
big turbo/high boost = smaller wastegate
small turbo/low boost = bigger wastegate
small turbo/high boost = smaller wastegate
However, exhaust flow is an effect of power. So, another decision chart could look like this:
big turbo/small engine/small power = small wastegate
big turbo/big engine/ small power = medium wastegate
big turbo/small engine/big power = big wastegate
small turbo/small engine/small power = small wastegate
small turbo/big engine/any power level = big wastegate -->The reason for this is that the small turbine will easily try to overspin from excess exhaust gas volume
Given this information, you should be able to draw your own conclusion