Conclusion
As you can see innodb_uuid_no_key performs closely to its integer counterparts, innodb_uuid_no_key_indexed exhibits the same trend as innodb_uuid to a much less severe degree and innodb_uuid_no_key_unique_indexed is nearly identical to innodb_uuid. So the unique index appears to be the issue here. But why? Well, given the above information, I’d say that MySQL is unable to buffer enough data to guarantee a value is unique and is therefore caused to perform a tremendous amount of reading for each insert to guarantee uniqueness.
What About MyISAM?
The MyISAM results were virtually identical (in scale) to that of InnoDB.