8gb is absolutely more than enough...
why would anybody need to store that much data on the phone?
that's what the Google Cloud is for, isn't it?
(the above statement is only true for people who have smoked too much pot or drank a gallon of vodka)
Because many like myself are throttled after 5GB or others that are on tiered data or shared family plans. Then there are those that get charged overages when they go over their allotted data. Cloud storage in this day and age is a good idea but not ideal when you have a limit as to how much data you can use. You also can't run apps from the cloud.
Now there OTG storage. While also a good idea why on earth would you tether something to your device to watch a movie or access stuff that you can easily store on your device? You also have the extra cost of OTG devices, then why not just pay for the extra storage? Doesn't make sense.
To sum it up, maybe an 8GB works for you BUT not for the average user. For a mere $50 it's a no brainer, get the 16Gb model. Also remember it says 8Gb but you're only getting a little over 5GB.