I have no experience with Yuki's 6542 case, but you should choose a case, in great part, based on the movement you decide to use. If you are going with a gen movement, then Yuki, NDT or JAW are the way to go & you must decide how much you are willing to pay for each case's set of inaccuracies. If you go ETA, I think your best bet is to buy a fully assembled rep & just replace parts (with gens or more accurate aftermarkets) as you see fit. From my experience, as long as the dial is fairly accurate & case is 'in the ballpark' no mere mortal will know the difference. As a perfect example, I used a cheap Silix Sub case for my ETA 2846-powered Phase I '42 (there are a handful of threads detailing the construction that you can search out) & there is really very little difference between it & the gen case I used for my Rolex 1036GMT-powered Phase II
(Phase II left, Phase I right)