I know the original factory loads are fairly mild compared to a lot of other big bore cartridges, but the newer loads for the 404 are substantially more powerful. Lets notforget that it is the most popular elephant round in Africa either. It just hasn't got all the attention here like the .416 Rigby, mostly because of Robert Ruark's writings about Harry Selby and his .416 rigby.
One can follow this argument at length by visiting ACCURATERELOADING.COM and going back a few years. Although the .416 Rigby is factory-loaded to very reasonable pressure levels, and can be mistakenly hot-rodded to much higher levels in most rifles, it is clear that the Jeffery is in the same league, at least in factory loads, which are about as fast as a sane man needs. The main advantage of the Rigby, aside from the name and the low pressure, is that .416 bullets are a little easier to come by in this country.
There is nothing wrong with a .404 Jeffery.