For Science!3 Reasons Soccer Ball Droid BB-8 Is an Inferior Design to R2-D2For Science! - RSS 2.0
But wait - it gets worse for BB-8. If an off-road vehicle does get one of its wheels stuck in sand, it has three other wheels (assuming four-wheel drive) to haul the load and get the vehicle moving. It can afford to lose traction on one or more wheels and still keep going. But BB-8 consists of only a single wheel - if he gets stuck, he's screwed. R2-D2, on the other hand, has three legs, and each leg seems to have at least two wheels on it. One wheel spins out or gets stuck? Many more to compensate!
Point: R2-D2, for having better weight distribution and multiple redundancies.
3. Fallback Options
If BB-8 gets stuck in sand, he can keep spinning and spinning in place forever without freeing himself. If R2-D2 gets his wheels stuck in sand, guess what? He can still walk! All he has to is execute his little hobble maneuver, move a few paces forward, then resume rolling. Or, if the surface proves too unfriendly for wheels, he can just keep hobbling.
And I don't want to hear any of that jet thruster nonsense - you know, those little side rockets that R2-D2 had in the prequel trilogy. First off, if BB-8 has those as well, then that still doesn't make him superior to R2, just on par with him. And secondly, using those rockets is obviously an incredibly energy inefficient form of locomotion, otherwise why even roll at all? Why not just fly all the time?
Now, I will concede that it is possible that BB-8 has some form of retractable legs to get himself unstuck. The teaser showed us very little. But I'm willing to bet that no such feature will appear in the movie - and that the movie will grossly misrepresent how maneuverable a self-propelled soccer ball can be.
Point: R2-D2, for being able to simply walk into Mordor.
By now, some of you you may be saying, "Oh yeah? Well you can't be right, because they built a working prop of BB-8 that actually rolls around!"
First of all, they did, and that is awesome. I could have sworn the BB-8 in the trailer was CGI, but I'm all for practical effects that are well-executed. That said, a prop is a far cry from the real thing. A prop only needs to perform under very specific conditions - conditions that are engineered to make the prop look as legitimate as possible. According to Making Star Wars, the prop was "allowed to roll on two tracks that [were] either obscured or digitally removed." And if you're rolling a ball on tracks, then you're engineering conditions that render my three aforementioned arguments moot while also confirming that there was a need to roll the prop on tracks to account for some unmentioned weaknesses. You know, like not actually being practical.
But hey. At least it's not Jar Jar.