I really like both, my opinion on the two:
ZT 560:
Heavier/bigger
more of a large sized folder, smooth
I like the 3-D machining of both sides
ELMAX: A good stainless, Edge retention will be right around maybe a little above S30V (although Kerhsaw/ZT tends to run their steel a little softer compared to Spyderco to gain toughness but loses edge retention), very stain resistant, tougher steel than 204P
- My 560 had excellent F&F, the blade flips open easier than the Southard, but I think that mostly due to the heavier/larger blade
- Have read a few posts of people that had F&F issues most were when it was first released, and were a very low percentage compared to how many have actually been sold
Southard:
- More of a medium size knife, although there is a lot of blade length for the overall size of the knife
- 204P will have better edge retention than ELMAX even if harder ELMAX
- Excellent out shallow cuts (rope, paper, etc) anything around an inch wide, it won't cut like a FFG Spyderco, but then again neither will the 560
- 204P is very rust resistant
- The action feels smoother/tighter tolerances than the 560, but the lighter blade doesn't provide the momentum in opening the 560 does so I'd say they're pretty even
- I have not problem with the pocket clip or the slightly different thickness scales (although I thought aesthetically it might but me at first).
- Haven't really heard much in the way of F&F problems overall if any.
- As far as Taiwain vs US manufacturing, at least from Spyderco's Taiwanese plant, of the two Taiwanese Spyderco's I have and the other 6-8 I've handled/looked at in stores all have had better centering and lack of blade play compared to US made knives from the the Big three (Spy, Kershaw/ZT, BM). Although I prefer buying US made knives, if given the choice between a US made Southard(Yay U.S.!) and Taiwan (consistently slightly better F&F) made Southard for the same price I'd flip a coin.
Bottom line:
If you prefer medium sized knives go for the Southard, if you prefer large knives go for the 560 and then get the other one later.