[Voronwe]

Well, personally I think it is almost impossible that they are the same person. The Lost Tales is not canonical - it was written early on in Tolkien's life and superceded by later writings. Legolas does not appear in any later version of the Fall of Gondolin (although these are shorter than the Lost Tale). Also, although Tolkien discusses Glorfindel (a relatively minor character) in depth, he never makes any mention of Legolas having lived on Gondolin. In any case the Legolas appearing in Lost Tales was stated to have remained in Tol Eressea. In all likelyhood it is merely a case of Tolkien reusing a name he had thought of long before. This happened on many occasions. For example the name Gimli was used of an elf in the original Tale of Tinuviel before it was transfered to the dwarf.