2003 Specialized Hardrock, 2004 LOOK KG386i, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1
You likely won't notice a difference. The biggest difference between cassettes is weight (and price of course). Buy the one that better fits your budget or weight goals. With chains, again you'll likely not notice a difference in performance. However, if you place on removing the chain for cleaning (as opposed to cleaning on the bike) you'll want to purchase a chain with a master link like SRAM, KMC, or Wipperman. Shimano using a non-removeable joining pin and breaking the chain requires installing a new pin (not a huge deal but more work than a master link).