My experience is with the 500gb models, and they are simply the smallest, most reliable, and error-free drives for USB Loaders. If you get the Seagate Freeagent Go, follow these tips in order.
Install Seagate Manager software (comes loaded on the drive) to your PC. If for some reason you delete or can't find the software, you can download it on Seagate's website. Connect your drive, and let windows fully recognize it, assigning it a proper drive letter. Then use Seagate Manager to set the power saving/standby to NEVER (now your drive will never fall asleep or freeze). Download the free program Compuapps Swissknife, and use it to format the drive to FAT32. Download WBFS Manager 3.0 and install to your PC. Open WBFS Manager, plug in your drive, press "refresh drive list," and select your drive letter from the pull-down list. Then press FORMAT, to make your FAT32 partition into WBFS. I strongly suggest adding a game using your PC first if possible, so drag an iso into the right hand box and select add. Plug it into your Wii, pick a loader, and it should work perfectly with no spin down or errors.
I highly recommend the Seagate Freeagent Go series to everyone. I have bought three now, and have no problems/compatibility issues at all.