Also, don't forget that any heroic ability bonuses will just keep accumulating while the guy is dead in the HoF. The guy you bring back might possess some.. strange qualities. Especially if they've been rotting in the HoF for long.
The following pic is from a ancient MP game where I was playing Machaka. When I researched Ritual of Rebirth, I noticed that my Giant Black Spider prophet (dead for like 30+ turns) was still in the HoF with his heroic strenght. When I brought him back, I was pretty suprised..
Note that the guy in the pic is suffering from the "weakened" affliction (real bummer, huh?). I eventually equipped him with 2x Sword of Quickness and a Jade Armor for eight 80+ damage attacks per turn for some epic SC slaying. However, he got sent to hell and never came back. Must have been that negative fire resistance..