The PAC jet is all about what happens near AK...you want higher heights around AK, like NCEP, EURO and JMA have. The French and to a lesser extent, the UK guidance are more hostile there. The westerly modoki la nina is more likely to have issues with the pac jet bc the Aleutian ridge is more suppressed and does not extend north into AK. The la nina events with colder anomalies further east tend to pop a ridge further north that extends into AK.
You are going to have a ridge near the Aleutians in a la nina due to the Hadley Cell configuration, just as you will a trough in an el nino...its all about placement of anomalies that determines the precise location/configuration, as Scott said.