hi malik,
ho reversion means that the MS was not able to connect to the target cell. After a short while, the MS (by itself) decides to stop trying and goes back to its old serving cell.
ho failure means the MS was not able to connect to the new target cell and not able to make a reversion.
also, depending on your vendor’s name definition, a ho failure could be due to target cell congestion.
cheers
pix