My opinion anyway.
My reasons are as follows....
First of all It's "profile" machining. Meaning it removes meat by dropping a slug. To remove the most stock, it has to remove the least.
Second it's accurate, and not just that, it's "predictably" accurate. As well as the time is very predictable helping out quotes.
Third, It's the easiest machine to program. Most things can be programmed in seconds.
Fourth, the tooling is cheap. The water gets reused, and if your clever you get your water from your AC unit's condensation, making it free. The wire is "if non coated" 30-60 bucks a roll, or 24 hours of machining. If your clever you can slow the wire speed down with no loss of speed or accuracy getting
30-40 hours a roll. A grinder wheel is a bit cheaper, but it rivals end mills.The operation is designed around unattended operation. It's easy to run 3-4 wire edm's per person.
Here's where it really can pay off. I have to use molds as examples because thats what i do... You can design a mold with no screw holes if you put tapers on the sides of blocks. You wire out the blocks with 2 passes easily holding a tenth, and you have tapers on the sides eliminating screw holes. Just the time saved in assembly is astounding, because you install the parts in the order shown on the print, hit the last piece with a hammer and its together. Tap that part out and it falls apart.
The machine lests a long time, since it moves so slow, and has no cutting pressures put on it's ways or screws.
Long story short, If your looking at moving forward and you have no wire edm...get one. It cuts the same hard or soft, and it can hold a finish as good as needed for almost anything,, easy to run, easy to program.
Wire edm rulez!