suggest you focus on checking how the car was maintained rather than buying if for features.

check the suspension well (you'll know once you drive the car into uneven roads) since unmaintained nissans usually have noisy suspensions

check the body. rust may have built-up on door hinges, engine mounts, trunk gutters, running boards, lower parts of the fender, etc.

check the interior - i'm not quite sure there's a super saloon model for the series 4 since the last super saloon is the B14 or series 3. anyway, if we're talking about the series 3, the SS has a better looking interior (more cloth) and has split folding rear seats. check these for damages. the SS also has a cloth ceiling upholstery which makes it more difficult to clean compared to the EX which has a vinyl (plastic/leatherette) upholstery that can be easily cleaned by a wet rag or any cheap cleaner. i think the carpet is also different so check this well for worn-out or damaged areas by removing the aftermarket mattings.

check the electronics - airconditioning and a/c switches, lights, wipers, wiper washer, rear defogger, interior lamp, power locks, power windows. take time to drive the car in a very warm weather. normally, nissan airconditioners can cool the interior of the car in less than 5 minutes (blower set at 2, thermostat set to 1/4, car with 5 occupants) in a very warm day, provided that the car was not parked outdoors. A/C of SS and EX are standard. The SS however has a heater function which we actually do not need here in the philippines, except perhaps during early mornings in tagaytay or baguio city

engine - Well, for one, the SS has a 1600 engine while the EX has a 1400. If you're into power, go for the SS. If you're more into fuel economy, choose the EX. noise level should be the same, unless the owner has made some aftermarket modifications like free flow mufflers and a racing filter that will make the engine 'louder'. check the engine for unusual/irritating noises. an unusual noise means additional cost for u

check the fluid levels and pipes for possible leaks - brake fluid and automatic transmission fluid (if a/t), power steering fluid, coolant reservoir, windshield washer, etc. there should be no leak whatsoever

check the engine itself for oil leaks at the top or bottom. oil "perspiration" or oil residue on the engine only means that you need to replace some gaskets (cost for u) and seals. you should not find any oil residues in a good, well maintained engine.

so as i said, everything depends on how the car was maintained. with this, i should say that the 20-40k difference for this model is really not worth it, feature wise -