Actually, the "best" is up to some heated debate! I know what David feels is the best. Others have the same feeling about Bradco - lots of construction sites have them on bob-cat types. Koyker also makes one that is sold into the private market and they are American made in, I think, South Dakota.
There have been some happy folks here with Italian hoe's. Forgot the brand name, sorry. The imported hoes tend to have lower quality in them and will have the strong potential for metric "oddball" fittings that may cause head aches down the road. Seal kits for the cylinders would be an additional area of concern. But with that said, the Italian made ones seem to be solid and there have been some good posts on the ones from S Korea. Stuff from China, well - I'd personally pass. A used Bradco hoe would be far preferable to a new China hoe, but that's just my take.
What ever you get, buy or build a sub-frame for it. The hoe is a lot more steady to operate than a 3pt mount. There is some extra slop from the mount.
Just for the record, What size are you looking for? A 52-ish Hp tractor can probably comfortably take a 10-12' hoe in the 2500-3000# range. The small hoe's are cheap, but the lack of reach, depth and power would probably drive you nuts. It would me.
jb