First the OP is 5'8" so heel strike is not likely an issue with the Crosscheck, especially as I mentioned in the other ongoing thread that several racks now allow for more rearward placement of panniers which solve that problem. Also, I doubt that there is a lot of difference in weight between a stripped down 520 and a Crosscheck and so the Crosscheck can be made to weigh more or less than the 520 depending on how it's built up. Both excellent bikes, but generally the Trek will come with a nicer paint job and be sure to consider any warranty.