Below 96% you are technically hypoxic. Hospital patients are automatically given supplemental oxygen if their blood oxygenation level drops below that. Of course you won't immediately pass out at 94%, but fatigue will become more of an issue the longer you are exposed to these levels. Alertness will decrease with time and you might exhibit symptoms such as lingering headaches and reduced field of vision.
90% is on the other hand already pretty low, depending on whether you're a smoker and your age and fitness level you might already be in danger of becoming severely hypoxic, something you definitely want to avoid.
I'd definitely hit the oxygen if I were you, if only to avoid the lingering headache that might keep bothering you long after you've reached your destination.
Cheers,
Dg800