Neither one nor the other captures the complexity. The duration of your trip is not the only factor defining if you are in low season; it is just one lever among others to manage budget.
You can very well travel for two weeks in peak season if you make compromises on accommodation or activities.
A third way, regardless of the season, is to focus on the specific experience you are seeking.
For example, I know Japanese people who go for a week to Kyoto during Golden Week to see the red maples, despite the high cost, because the experience takes precedence.
Duration is just an adjustment to reach your goal, not a seasonal inevitability.