I am a ZT 0200 fanboy. I think it is awesome, overbuilt, and generally amazing. my recommendation goes to it immediately because i have not had the pleasure of handling either of the other 2 knives. however, i am assuming that steel matters becuase it was in the title, so here goes.
154cm, IMO, if more than fine. it can probably be argued that at least the S30V would hold a better edge, but i find that the 0200 was very adequate for EDC. I have been carrying it with my S60V blur for about the last 5 months, and i alternate between them for cutting tasks. It has not yet needed to be sharpened, but has been just because 2 days ago. in that amount of time it did many every day things, cut a lot of plastic, and went through 4 1/2 inch branches, thinned down the tips, and still had barely lost any sharpness.
TLDR, 154cm will be just fine, S30V will be just fine, have no idea about ats34. recommendation goes to ZT 0200 for quality.