VHBL is basically just the PSP's Half-Byte Loader, which is basically useless if you can install custom firmware as the HBL (or Vita HBL) only runs stuff that was made to support it. Not much supports it though as you can just run everything if you have custom firmware, which any PSP can get. The Vita also has Retroarch, which can take advantage of all the Vita's extra hardware to run games better.