You mentioned you have unequal entries in both lists, now assuming all enteries
in the shorter list are available in the longer list then it should be quite
easy if you take the longer list as the key in the Vlookup suggested by Ray.
However If you have unique entries in both lists then you'll have to go through
the second list again with another vlookup (there may be a simpler way to do
this) to identify the unique entries and copy them to the merged sheet.