I debated this same issue recently; my need is to have space for video from my GoPro. In the end, I decided that I can just carry a pile of SD cards for the GoPro and not worry about downloading them until I'm home. I could not find a tablet that had sufficient storage space available to make it a storage device on its own, and carrying added gear negated the size advantage of the tablet versus the notebook computer. Uploading via wifi to remote storage can be slow and is dependent on finding a hotspot (which are seemingly absent out in the backcountry
). When I do find a hotspot on the road, I'm usually not inclined to sit and upload hours of video files, I usually just check in with email and such and get on my way again. I can hotspot from my phone as well, but moving large files would end up costing a fortune in data charges, and again is dependent upon a cell signal which is often absent in the backcountry also.
My final decision: I got a Nexus 7 tablet as it is small enough to tuck into my tankbag for travelling. I'm watching the sales for good deals on SD cards. Quite often the 16G class 10 cards come up for under $20 and sometimes for as low as $12-14 for good name brand cards. I have about six all ready and figure another 6-10 will do me.