Aftermarket springs tend to be a little stiffer. The benefit (at least in theory) is better disengagement of the clutch. If you're hard on the gas this could help. The stiffer the springs the harder the clutch pull will be, but unless you have tiny little girl muscles this should be irrelevant.
Clutch stack height is important, but I wouldn't base the proper thickness on a worn out clutch. Hopefully your new fibers will be thicker than the trash you are replacing. If you are concerned, you can measure all the steels (they come in multiple thickness, you'll need a caliper or micrometer) and ensure you replace with same. Most if not all will be the same. You can also fine tune the slipper using different steels.
If you are on a budget, you may be able to reuse your steels. Clean them up and inspect to confirm. I always replace with new fibers, but I have seen good steels when fibers were shot.
Make sure you install all the steels the same direction. One edge is smooth (rounded), the other square.
Soak your fibers in oil before install. I do it overnight, but an hour or so should do it if you are in a hurry. Use the same oil (clean) that will go in the bike. I use those big aluminum pans for baking. Some foil over the top and you can save it for reuse.
Nothing wrong with OEM. The major aftermarket players are good as well and can sometimes be had relatively cheap via ebay.
ccasion1
