Is it worth $100 to me? Nah. To you? Who knows... But if you are considering $100 being a big factor, probably not.
High performance? Yeah, probably just a little bit. You should google the cpus with the term "benchmark" in there and find some results. I bet they've been compared.
i've built a few x2 rigs thus far for customers and can say that the 4200 and the 4400 have nearly identical performance. that is, to say, the the difference cannot really be noticed. the biggest differences are between the 4200/3800 and the 4400/4800, the latter being the bigger gap.