Tim, naturally I think the hydro is best for using a tiller, but if I remember right, the manual for my Bush Hog tiller mentioned depths you could expect on 1st and 2nd passes at 1 mph.  My tiller was a chain drive, 4 tines per row, and was used hard and even abused for over 7 years and never had a problem with it.  The chain ran in wheel bearing grease instead of oil.  After a couple of years, I cleaned it all out, replaced the grease, etc. (manual said every 100 hours), but it really didn't look like it needed anything.  Then just before I sold it, I pulled the cover to service it again, but it looked so good I didn't even do it; just put the cover back on.  I experimented with different speeds, but think the 1 mph is about right (estimated speed of course since the tractors had no speedometers).  I can't imagine a tiller doing a much better job, but do think, without knowing for sure, that a 6 tine tiller should do as good a job at a little faster speed.