Paul,

The first formula lets the function multiply the two arrays together, as SP
was designed to do.

The second multiples the two arrays by use of the * operator and passes the
resultant array to function as a single array, which SP can simply SUM the
elements, so it does not use the product part of SP, just the SUM part. In
that respect, it is redundant.

The operators in SUMPRODUCT are usually used when conditional tests are
introduced so as to resolve TRUE/FALSE arrays to 1/0 arrays that can be
summed.

Have you see this page http://www.xldynamic.com/source/xld.SUMPRODUCT.html