[sv-bc] What's the difference between "let P = const_expr" and "localparam P = const_expr"?

In the proposal for Mantis 3295 there's code

   // now define lets to make the code more readable
   let LOCK = 1;
   let UNLOCK = 2;
   let ON = 3;
   let OFF = 4;
   let KILL = 5;

that looks a lot like

   typdef enum { LOCK=1, UNLOCK, ON, OFF, KILL } dummy;

or

   localparam LOCK = 1, UNLOCK = 2, ON = 3, OFF = 4, KILL = 5;

Is there any practical difference between these different ways of defining local constants? Is one way preferable to the others?

'let' can do things the others can't, such as stand for a non-constant_expression or take arguments, but for constant_expressions and no arguments what are the differences?

-- Brad

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