In the past, OSL and ARN were equivalently priced, and ARN has two hotels inside the airport, making it easy to schedule the positioning flights with an overnight and not need to bring a coat or anything warm to wear even in winter. I believe the closest hotel in OSL still requires walking outside for long enough that not having a coat would be impractical. I try hard to never check bags, and bringing a coat would be a problem on an itinerary that otherwise goes only to warm places. I may have to work harder to schedule same-day turns for the positioning flights or check a bag and brig a coat.