Of those two the 405 is the more sophisticated watch, with more advanced features. The difference in price on Amazon is only around £30 as the 405 model is older (replaced by the 410), but at original retail it was a lot more.
As Fiona J said, the interval function was the decider for me. I went for the 405 and I understand the criticism of the bezel, but its easily avoided by locking it during runs.
You haven't given any details of what you'll use it for, so its hard to judge for you. If its to track your runs then the 110 is enough, but if you want the watch to assist with more advanced training plans the 405 is better suited.