Maidsafe seem to be ahead in the development stage.
How so?
Check their progress and number of pull requests, the work done has been massive.
I still don't see a working beta or anything though. Storj recently launched its first beta, and you can see those distributed farmers here:
https://live.driveshare.org/Then again, it's all about cooperation. No need to back one or the other - Storj and MaidSafe plan on some amount of integration with one another.