The PI should be newer (released in September 2008). However it looks like the HK has been updated (lower voltage and different timings than the previous version). The PI has better heat spreaders, but if you don't overclock, the HK should be as good and it's less expensive.
I don't know. You could contact customer service and explain the height was a problem. They may. Those tall HS's definately will not work in my Micro builds. Maybe just ask to return it for that reason. Then buy the other one on your own.
I was able to get a refund from newegg but before I return the ram I would like to know if the blue sticks will be short enough to fit under my heatsink fan. Do you have the measurements of the height of the ram?