A:Answer This question has probably been answered for the satisfaction of the op, however for future questioners it may be beneficial to answer the actual difference between the drives..
The {G25} is the type of drive, and therefore both will be the same performance, mtbf, etc.
The main difference is that the 500gb drive is a 4k sector structure, and the 512gb drive is an 512b sector structure..
512b storage devices of any kind will have a storage capacity divisible by 8 and typically increase by a factor of 2xbase, so 8gb, 16gb, 32gb, 64gb, 128gb, 256gb, 512gb, 1024gb, etc.
In general there will be no significant difference between the sector structure, perhaps a sight difference between lost mb's when formatted.. The 512b storage devices will generally lose a little less mb when formatted due to being easier to round off partition sizes given the smaller sector size.
However there is a legacy difference in operating systems such as Unix, and variants like Linux, where those operating systems were designed to expect 512b sectors and all but the newer kernal versions of Unix variants may have trouble installing and/or managing 4k sector drives..
If you do not plan on using Unix and variants, or do not plan to replace a drive in an older Apple computer, you will likely have nothing to worry about and can purchase whichever gives you the most mb/$.
