Use free JNX and you will be free from all limitation!

number of levels of detail: JNX up to 5 KMZ - only one
number of tiles: JNX - up to 50000 per level KMZ -max. 100 per device (!), up to 500 in Montana
subjective rendering speed: JNX - high KMZ - low
supported image type: JNX - any type KMZ - Jpeg
image size: JNX - up to several Gb KMZ - 3MB