That is a very good burn. Look at the PIF levels. 328 with a max of 2? That is really good. The PIE readings show some high spikes, but those can be disregarded as a general rule. Average PIE is also good. I'd like to see a TRT scan as well, but I suppose that isn't available.
They are using 16x TY +R in that scan, which is a type of media we often recommend around here, so a good scan from it is not surprising.
USB burners draw more power than the 500mA that the USB 2 interface allows in its specs. This overload can cause problems, including burned out usb ports. Also, the slim drives have a history of self destructing faster. They also have fewer firmware updates as a general rule (though LG is notorious for not putting out many firmware updates for most of their drives).
The slim drives also burn slower, as you've noted, and many types of modern media burn well near their rated speed. If you're using excellent media to begin with, you may not notice this much. If you are using run of the mill CMC or Ritek discs...it may mean the difference between an acceptable burn and something that fails quickly.
We've been watching the general trends in burners for well over a decade here. What I'm relating to you is simply common knowledge in these forums. A dozen or more members here could have told you the same information.