I have recently purchased 309 and its pretty good. I too was in a dilemma whether to select MAX or 309 but went with 309 because of 2 main reasons..
1. The features are similar except for 2 to 3 differences(which i didn't find too important)
2. Slider phones usually end up having problems with the sliding mechanism after some time.
I didn't find it worth spending 1000 bucks more and then having to take extra care of the phone.