How to Disable brand logo and boot animation
You can delete /system/media/bootanimation.zip and the second boot animation would be gone. You need to root your phone to do that though. Also, this would make your home screen appear faster, but not fully functional until it competes boot.

Changing or removing the first boot splash is trickier, it requires recompiling the kernel with a blank boot splash and flashing that to the device - which is dangerous, hard and , as it requires you to unlock the bootloader, possibly void the warranty and it also runs a risk of bricking the phone.