* Charles is quoted & my replies are inline below :
Kenko is cheaper, anything else to consider? I just want to reduce
minimum focusing distance.

The full set of Kenko tubes gives 36mm + 20mm + 12mm. Canon only
comes in 12mm and 25mm. So you can get higher mag with Kenko
full set.

There is no glass, so to me the quality is less important - they
just provide more space between lens and sensor. Mind you, the
quality isn't bad.

Don't know what lens you have, but if it's EF-S make sure you get
the right tubes. The newer ones will AF for EF-S lenses, the
older ones didn't.

That's all I can think of for now.

--
Troy Piggins
Please feel free to provide constructive criticism on any photos I post. I'm
always learning and appreciate feedback.