I don't own the Hitachi, but I do own the Wanachi and I will stick to my original review. This is by far one of the most powerful toys I have tried that requires batteries. The power is equal to the California Exotics Larger massager's, but I can't compare them to Hitachi. (I guess I really do need to get a Hitachi, so I can compare.)
The Wanachi does rattle with noise and it is super loud. It is less bulky of course than the Hitachi, but the length does tend to get in the way unless you are on your back. Overall Wanachi is well worth the price of less than $20! And it comes in a pretty color selection!