I read some good reviews of the Hakko 936 when I was looking, and it is priced better than the WES51 (regular pricing). Feature-wise they are comparable. The deciding factors for me were;
(a) promotion negated the price difference,
(b) a local store sells Weller and carries the tips,
(c) I was able to examine the iron before buying it, and
(d) instant shopping gratification!