Boy, I typed a long answer... read COW, Filmjackets.com and IndyLounge for the details of how all 4 jackets differ.
Specifically Wested. They have 2 tiers of jackets. OTR and Custom. OTR are made in India. Custom in the UK.
They have 2 styles of Raiders of the Lost Ark jackets:
1) 'Raiders', this is a corrected sturdier pattern, it has leather facings on the zipper to make it more 'finished'. It's assumed to be less screen accurate.
2) 'ROLA' this has most of the detailed specs fans ask for, narrow yoke, closer fitting silver zipper etc.
If you are slim the ROLA may fit you better than the RAIDERS.
Then they have Last Crusade and Crystal Skull patterns.
Imo, look into getting a ROLA custom. Read up on the details included and then see if there is anything that you really NEED it to have and make sure you specify that. ie silver zipper, or a narrow yoke with rear sleeves seams falling below the yoke.
The Temple kicks butt too IMO.
There are lots of leathers to chose from and you will have to look at them to decide. New cow and horse whilst tough, do not hang like the original trilogy jackets which were all lamb. (there is some debate about the LC!). A interesting compromise is washed goat with is thin but tough. It has a very matt finish that puts some people off but it ages to something quite nice quite quickly.
A little reminder as to what the Raiders really looked like:
http://www.youtube.com/watch?v=7hnGvH72S3c
