Where do you hand in your completed books?

Basically which EOTN title hardest to farm?
This weekend I did a bunch of random farming / vanquishing and got my EOTN titles to r6-7 and r9 delver.
But im wondering which is the most tedious / takes the longest to max out?
Currently I have a full book and 2 more to come soon, and was wondering which title I should donate the books towards.
I havent really done the farms listed on wiki for each title (besides the snowman farm), so I dont know which is the slowest.

So, what yall think?

I don't know about the slowest (although my guess is Ebon Vanguard), but I turned mine in for Asuran because I wanted more rank for Pain Inverter.

I've been turning in both books for norn, asuran, and vanguard to get them as close to 80k as possible. Next one set of hm for all except delver. I havent turned in anything for delver since the 1st book because its so easy to farm points with snowman and I was doing duncan.

Gunnars has the delver & norn, eotn has vanguard, and Rata Sum has asuran. Tyr the Skaald (Norn), Kodan (Deldrimor), Lexx (Asura), or Gedrel of Ascalon (Ebon Vanguard)

http://gw.gamewikis.org/wiki/Hero%27s_Handbook