Gen2 Shield TV 16GB vs Shield TV Pro 500GB

I am planning on purchasing a Gen2 Shield TV (been wanting one for a while but held out for CES because rumor was they'd be revealing a new and improved shield) and am wondering, besides the 16gb vs 500gb, is there ANY difference between the two? Like any at ALL? I was just planning on buying an external HDD to plug in to the 16gb shield and use that as my storage, but will I run into any trouble using that instead of the internal storage? Going to Vegas on the 26th and would love to bring one with me, but if there's more differences between the gen2 shield and shield pro besides the amount of storage I may just say screw it and wait till the Shield Pro releases on the 30th. And like I said, if there's gonna be any issue using an external HDD with the Shield instead of internal storage I'd prefer avoiding those issues all together and getting the Pro.

But if none of those things will be an issue and the difference is simply the storage id much prefer just getting the 16gb and adding an external HDD

So what do you guys think?