I like the Black Widow stringer for recurves, but I like the Selway stringer better for longbows. Sometimes the top nock cup on the BW stringer (or any other two cup stringer) slips off the upper tip of the longbow because the longbow tips are pointed down when in braced position. Believe me, this will wake you up if it ever happens to you! The block on the Selway prevents this from happening.
I've never tried the Thunderhorn, referred to above, so it could be even better as VI Archer thinks it's better than Selway.
Frankly, I prefer to string a longbow with the push-pull method, unless it has a lot of reflex/deflex, then I prefer to use a Selway.