I would take the default if I thought I had a good chance to beat the guy. Otherwise if I was a massive underdog I would not take the default.
Presumably there is nothing to gain by winning/losing other than placing on the ladder... so ultimately the real goal is to find your true 'slot'. No point in taking a default and taking an unrealistically high position only to end up getting dropped again when you lose to people below you.
On the other hand, maybe I would take the default after all just to punish the guy for feeding you obvious bullsh*t.