If you have the extra 100 I would go i5 2500k As far as the new processor is only a dual core so it will take a performance hit and your cache is lower and you are going from a 400 dollar cpu to a 125 dollar one so I dont see the point in buying a i3 try the i5 2500k and an asus p8p67 pro for about 100 dollars more than that cpu/mobo
The real question here is, better for what? Like the above poster mentioned, quads, in general are better than duals, and more cache is better than less. However, depending on what you plan to use the machine for, an increase in clock speed like that could make it worth it.