Don't be fooled into thinking that a five-port will automatically trounce a three port, because this is fundamentally not true. In theory, a five-port will rev higher and easier and thus produce more power at high revs. It, again in theory, should be more peaky as a result.
Both my team and myself have experimented with three and five port novarossi-based engines, and the latter do produce more power...but only just. A properly tuned three-port turbo isn't that far behind the five-port varient when it comes to ultimate top speed. In certain situations (such as a very tight track) a three-port could actually be the quicker option.
Five-ports do produce more power, but not on the scale of "If i replace my three-port with a five-port, will i be able to handle it?!"