resale value will be the same on both types if you're selling them with the car ST's are expected to have them as standard so no increase in resale, but if selling them seperate to the car then genuine will fetch more money.
There are replica ST alloys based on the Mk2 design, the design differs on the mk2.5 but theres no replica on the market matches the mk2.5 design,
The replica alloys are a universal fit meaning the accept different sized spigot rings allowing fitment to non ford models aswell as focus they are also 18x7 or 18x7.5 finally they may or may not have gone through European safety checks possibly manufactured in china where the build quality is a gamble buyers risk and no real come back check ebay sellers terms.
Genuine facelift ST alloys have a centre spine on the spokes,
They dont need spigot rings to fit the car,
Ford supply them so your guranteed safety checks have been met,
They will be 18x8" and 200 a piece is 75 pounds cheaper than i got mine from ford, Manufactured in Germany
Tyres and centre cap seperate.
Heres some pictures of genuine facelift ST alloys
If fitting 18x8 to a non ST model and you plan to lower the car on ford approved eibach (ST fitted as standard)
you will need to purchase a steering rack limiter kit from ford, it costs under 30 pounds and prevents the inside tyre wall from rubbing the inside arch guard on the car,
Consists of two polyurethane rings one fits inside the cv boot on either side of the car,
If lowering the focus 35mm you will require adjustable rear camber bolts cost under 40 pounds on ebay,
Prevent negative camber after lowering which causes excessive wear on the inside of rear tyres as saw in image: