If you have a single segment turned on at once, and mux through all the digits with just one segment turned on and the illuminating current sunk through one resistor, there's really no disadvantage at all, as the brightness will be quite consistent.

I've seen all manner of schemes used for lighting 7-segment displays, and one segment at a time has always worked the best for me when I had time to do it. The background task takes a little more time, however, in that you have to AND the current segment with the current segment map for the current digit's value. If you give each segment the same amount of "on" time, it will be as bright as any other segment that's turned on, and you can treat non-illuminated segments in the same amount of time.

I'd say it makes everything simpler. What's more, you don't need that annoying inter-digit pause that many people like to use.

RE