Disclaimer: I am fully aware that this question may come off as too broad or opinion-based.
Here's the character in question: https://docs.google.com/spreadsheets/d/1bYcgjyeuXGZnj_1Bht-n2c5nRMxtNRsfPB1Nm243xic/pubhtml#
Summary: He is a rapier-wielding warblade, played more like a swashbuckler, not an optimized all-out death machine. I already took Improved Initiative at level 5. So now at level 9 I am looking at the following two warblade bonus feats: Combat Reflexes and Iron Will.
Campaign Background: Mid to low magic campaign. Combat and role playing oriented. I suppose thinking back Will saves come up more often than AoOs.
Combat Reflexes: Let's me have more AoO. I have a DEX mod of +3, so would give me two more attacks. Ends fights quicker, makes him more dangerous, provides more combat choices/options, and in theory more fun.
Iron Will: Will is one of the character's two biggest weak spots (the other being ranged attacks). This would directly address one of them. But it's a boring static bonus. But then again being mind-controlled or sleeping or confused isn't fun either.
The big question: Will my overall enjoyment of playing be increased more with Combat Reflexes or Iron Will? I think it comes down to CR adds versatility while IW addresses a bigger weakness.