so, i was looking at purchasing a 200 GB HD 7200 RPM and I saw there is a 1.5 GB transfer rate and there is a 3 GB transfer rate. I see that in my system profiler that the HD is current a 1.5 GB and a 5400 RPM. Would it be safe for me to get the 3 GB transfer rate one or should I stay with the 1.5 GB?