the uk hotter cams, Piper and Autosprint, make the engine more lively at 5.5k on imho, certainly stops that 'hitting an acceleration wall' feeling where the cars acceleration feels to drop off even though it will happily rev out to 6,5-7 no problem. may be more noticeable in my car as it weighs almost half what an s12 does tho
S13/14 boxes are essentially the same externally bar the bell housings, but the internal ratios are different as is the oil system design.
the uk and overseas boxes have different ratios so check what you have (also turbo and non turbo cars have different ratios, not all of which we get here).
The best box is the later s14 box, s14a here in uk as this has a centre trap door system to stop oil surge. The s12/13/14 boxes are all from the same family and as they get newer they get fewer oil holes in the centre steel plate between the alloy bell and alloy tail sections. The oil tends to all run into the tail casing under hard accelertaion and starve the bearings gears synchros etc. the s14a trap door stops oil rushing to the tail housing but allows it to flow back under braking. im sure i have pics somwhere of the differences if you need them.
Check which you have, you can always block off some of the oil ways with JB weld and make a trap door if its necessary for your usage.
The s14 (uk) boxes are closer ratios, with a fair bit taller first, then slightly taller 2nd and 3rd. 4ths the same but 5th is shorter (giving marginally lower top speed).
again check what the ratios are available where you are and work out which gearset suits your diff ratio/usage and tyre rolling radius.
CNH