What's the best container to ferment vegetables?
I've used the harsch crocks myself - for longer ferments (3-8 weeks).  However I've used the giant glass pickle jars for beets when making kvas for borscht.  

The thing with the harsch is it takes the guessing out - once you seal it you don't really have to worry about anything except keeping the little water lip filled. 

Fermenting in glass jars, to me, has been much more high maintenance:  you need to top off water, skim the gunk, make sure that it doesn't go bad - but I've used them successfully for shorter ferments (7 days versus 6 weeks).  One thing I'd say about the jar ferments is you need to make sure that you've got enough salt in there - this method to me is way less forgiving and goes bad easier.

Good luck - fermenting on your own is soooooo worth it.