Eliot coleman (in ' the new organic  grower') has a pretty strong preference for the smaller wheel, not the high wheel hoe...  he talks about the biomechanics of it being much better with a lower center of effort.  I haven't tried either.
 
  Lehman's has three different wheel hoes for sale, i am thinking of the small wheel with the scuffle / knife attachment..
 
 
small wheel hoe
  
 
 
  I also use a single-horse walk behind cultivator which fills a similar role, but i think a wheel hoe will have it's place when the spacing starts to get tighter..
 
  There's still a time and a place for planting in rows on my place, but we've all got different contexts to work within..