You can only judge if an index is well-used if it has some statistics (about hits and updates). If an index doen't exists in the DM view, it doesn't say anything about it's design. It's just telling you the related table was not referenced in a query since the startup of SQL.

Try this (but not on a live environment!): restart sql and run the "large" unused index query, you'll see almost every index will be reported (because nothing happened on the database so far). If you run the query again after some time, the number of unused indexes will decrease. Does this tell you something about how usefull an index is? No.

To conclude: regardless which script you use, you'll have to compare the hits against writes to determine if an index is useful. Make sure every batch has run against the database in order to get a complete picture of your database activities.