MySQL with Cache faster like H2 In-Memory Database! Why?

[snookerms]

Hello,

I have a question. Why is a H2 in-memory database slower like a MySQL 
Database. The database struktur is in both the same, the index,too.

But Benchmarks show me, that a H2 in-memory database is faster like a MySQL 
database without using cache. Only kex_buffer_size is used in MySQL.

When I use query cache the MySQL Performance is better like the 
H2-In-Memory Performance.

Can somebody explain me why?

I thought a In-memory database is allways faster then a disk-based 
database. But my Benchmarks show me, that a disk-based-database with cache 
is faster like a in-memory database.