As a person who actually sells garden tools the following applies.
Steel hoes have a toughened edge - this applies to the first 5 to 10mm depending on the quality. These will only need to be filed to a "edge" once a season for general use, the "edge" is regained whilst in use with a small oil stone (70x25mm) and a light duty oil such as 3in1. Needless to say the hoe needs to be kept clean and wiped over with an oily rag after each usage (if you can be bothered!)
Stainless steel hoes are much the same BUT they are not really true stainless steel as this would be too "soft". If my memory serves me well garden tools of this ilk have a higher nickel content (than say stainless steel knives and forks etc..) Its true that SS needs more maintenance in retaining an edge but you can acheive a good high "edge".
The best hoe in my opinion is a SS one produced by Wolfe-Garten.