I have both. Sold echo (had 2 ...from drops 1.2k dps no sockets though). WKL is better if you play FoT and SW cyclone. Can really see the diff when you ahve at least 6% Lighting damage/ 23-25% lightning skills.

I hated echo becasue of the fear. Mine had quite high fear rate (16-18%) so... mobs keep running away which is not very good if you are a tanking monk. But Echo has a nice +0.2X attacks, which will add to the offhand, i.e if offhand is a mace, it will be 1.2 +0.2X per sec. so dual weilding will be very good. Paring it with WKL or Buring Axe of Suckis (sarkis)..is very good as you get the additional bonus for the +min damage + max damage.

The problem with WKL..is low DPS..getting a WKL > 1k DPS is very rare. Really good WKL, i.e 9XX DPS socket + LSi with nice bonus (6%, 23-25%)is pretty expensive but to me its will be best weapon (offhand) for a monk on Fot / Sw. Also you can consider Buring axe, just change SW cyclone to fire...got life steal ...nice!!!!..watch them burn and you gain life..

Yup. WKL mostly as offhand as DPS not high enough to be main. If go WKL as off hand ..for the mian hand make sure you get highest damage range (the little number thats says 600-900 damage) and look for +min+max damage as the 5-6% bonus will apply. The 5-6% bonus will not apply to elemental damage  eg like +300-600 poison damage).