Some numbers from comparing Memcached with InnoDB Memcached in MySQL 5.6:
Keep in mind that the entire data set fits into the buffer pool, so there
are no reads from disk. However, there is write activity stemming from the
fact that this is using InnoDB under the hood (redo logs, etc).
There is a significant impact on the speed so deciding which solution to use gets down to analysing the costs and complexity of maintaining another tool, the cost of Memcached warmup and the performance drop of using InnoDB Memcached.
Original title and link: Memcached vs InnoDB Memcached in MySQL 5.6 ( ©myNoSQL)