10 speed is the way to go for road groups. 9 is still going to be available for a long time because there's a lot of it out there and it's reliable... But it's slowly losing ground for parts availability at many shops, outside of chains and cassettes. If you don't mind having to order parts, then 9spd is still a strong option.
In the 9 vs. 10 argument, consider the crankset: is it a triple with the 9? Is it still a triple with the 10, or backed off to a double?
The Defy is a really sweet ride, so if you can get a deal on one, go for it.