I know this is a matter of major debate, so I just thought I'd offer you some thoughts.
You don't have to buy the body pillow AND the pillow-case, just the sheet. I mean, I'm assuming you already have a bed.
At ¥10,000 ($101 USD), they're cheaper than most of the body pillow cases out there, by anywhere from $20 to $100 bucks (minus the cost of the pillow, see above).
You have more possibilities for the art!
- Already basically the same size as a full American bed (210x140 centimeters)
They seem to be just printings of art you've already seen, whereas the pillows get their own special art. And are double-sided.
Are perfect if you have a full-size bed, but too big for a twin and too small for a queen or king.
Harder to take them with you to display at cons.
You have to get rid of your old Teenage Mutant Ninja Turtles sheets.
Okay guys...this is it. You need to make your choice. Dakimakura...or hot bedsheets?