This post contains spoilers. sorry.
I went with HoA. I just loved the feeling of revalation that we got with it being the last book of the series and all (i guess i should say most) of the secrets being brought out into the open. Even though a year of speculating led me to guess a few of the reveals, most of them came as a surprise and i was wowed.
We had Spook turning into one of the coolest characters of the series, TenSoon giving us a fascinating look at kandra civilization, Sazed and his struggle with faith, and some of the best fight scenes ever (Vin versus thirteen Inquisitors comes to mind), though granted i think the best ones are in WoA.
The only real problem i have with the book is that the Vin and Elend character arcs didn't seem quite as strong this time around, which is, i think, one of the reason it was ok for them to die at the end of the book. I felt that the first two books did a great job of exploring their characters and showing them grow and so by the time the third book came along there were only a few loose ends to tie up in their relationship, and then they were "ready" to die. But i think it works out. That fact allowed us more time to explore the other characters of this world.
All in all, HoA was epic. A great conclusion to a great series.
(P.S. WoA is a very close second)