As Oct said, the new Kenko set does support efs lenses. Thats the same set I have.
One issue to consider is, you really lose DOF (depth of field) when using extension tubes. macro shots already have tiny DOF. Tubes make it smaller still.
As far as quality, kenko vs canon. Its a no brainer. Go for kenko You are only adding hollow tubes - no lenses/glass. IQ will not take a hit.
You are also getting 3 different sizes with the kenko, and they can be mixed and matched for varying sizes.
Hope this helps.
johnny