A hard reset is when you restore your phone to factory settings and erase all user data. A soft reset is when the phone is rebooted or restarted, like when you select restart on your PC, but all your data remains on your phone.
Soft Reset clears out System RAM and solves some minor glitches.
Hard Rest restores the phone to the last OS/Firmware flashed and solves major issues (Hopefully). I think Hard Reset is OK, but if you need to go there why not just use a reset tool like WPRT? I'd prefer a clean install over a recovery partition. You may get a needed update in the package and you may avoid a bad file in the storage.