The ERC1155 standard interface has a URI (Uniform Resource Identifier) that can point to a file where you can specify all the characteristics of the token (name, symbol, description, size, color or whatever you want).
On the other hand, ERC721 standard interface has only name & symbol, but there is also a metadata extension (
ERC721Metadata) to use also a URI with additional data.
Having this metadata URI gives you a lot more flexibility to define all data you may need about the token, besides name and symbol from the original ERC721 specs.
Therefore, the difference is that ERC721 was originally defined to use only name and symbol as mandatory fields and URI extension as optional feature, whereas ERC1155 came with the URI by default.