Differences between Izoard XP 2013 and Izoard XP 2014?
Annual improvements in bikes tend to small and incremental. They have been doing this for over 100 years, unless someone comes out with something revolutionary, its hard to see how they can make a big difference. If it is revolutionary, it won't be the same model name (and it wont be 105). 

For me, a grand in the wallet makes the 2013 a better bike. In a year, the 2014 will be a grand cheaper and in two years the same price on the second hand market as the 2013. If I wanted to spend $3000, I would buy the 2013 model of a $4500 bike.  

Only you can decide if small incremental improvements are worth the money to you.