The-+ = + Video Storage Capacity obviously (while traveling or even on the train / metro etc ... it's always a pleasure to watch a short video, a clip or other ...)
The - = if you look at videos and you stop reading to look at another and so has a rate close enough, the battery does not like AC and will empty relatively quickly!
-A bit expensive but hey, it depends on your use! I personally use it every day so the price is depreciated (however I use + for the music for videos even though I sometimes watch videos podcasts quite often.)!