SGP far better. Performance over a season is a better judge than a one off Final where a bike failure or thrown chain can ruin hopes. Also some riders would be favoured by certain tracks. One final at Bydgozcz and you may as well give Gollob or another pole the trophy. Conversely a class Pole hasn't won at Cardiff but Chris Harris has.
Opportunity to see riders try different tracks, to travel to different cities, see speedway in other countries, one bad meeting doesn't harm a total season's work.