Bill Tindall, E.Tn.
There is no practical reason to own a brace and bit if you have an electric drill and various wood bits for it. The pricy 3/32" to 1/2" set from Lee Valley is a purchase I don't regret. The common sizes of screw lead bits for farm work are inexpensive and drill fast. For some occasions the compactness of the electric alternative is essential. Try drilling a hole in a floor joist on 12" centers with a brace and bit for example.
I used to use a brace for drilling holes on the farm remote from electricity. About 15 years ago I bought a battery operated half inch drill and have not had any desire or need to use the brace since, for drilling holes. A screw lead drill for an electric drill is times faster in a fence post. A lipped/spur wood bit in an electric drill is again times faster and leaves a smooth hole with no chip-out on the entry or exit.
On the other hand if you just like using tools that don't involve electricity go for it. We can't make that decision for you. New shiny inexpensive brace bits can be found readily at old tool sources because they are not in high demand.
Now for precise control driving or undriving square head screws, the brace is tops.