RE: What are big bore shocks?
Very astute question...For most they are nothing more than a placebo.
If you have an old (for example) Mugen MBX5, with standard (I think they were 14mm) shocks, upgrading to the 16mm MBX6 shocks will definitely make your suspension more plush. Whether or not it makes any real difference to anything, perhaps, but only at the very top level of racing. One of the main criticisms of the Xray cars was that they were slow to fit their cars with 16mm shocks as standard, so I guess it is something that racers feel that they need in order to be competitive. Durability, well depends, if they have thicker shafts than the originals, potentially yes.