It's better at doing damage, especially quickly, but it's more expensive. Firing five coilguns, or far worse, Plasma guns, is damned expensive after a while. I think the best tactic is a mixture; fire the big guns and take out anyone with a rifle or better, then close and finish them off with swords--and eventually powered katanas. That way you won't take much damage requiring tendstims, which are also kinda expensive (one tendstim is 1.5-2 shots with a coilgun) but you'll save money on ammo.
Really depends on the weapons. (& sadly, *WAY* too much randomness!) As you say, Coil or Energy's very expensive. (should be!) In other runs (prev to 812)
did best with Crafting Coil ammo (you can't craft Energy, & @ $500+, it's not really a $ practical weapon!)
if you have the stats (apart from luck/randomness, STATS R next best thing) Kat's are best (melee) I've seen them match Coil for dam, & on average (assuming *NOT* bad luck!) = or better Dam than MG! Make sure you use Combat Weave AR, as anything else kills Dex (more likely get hit!)
If you doing Melee, swords (13 dam) are just too dam weak again hi end weapons/enemies. Kats (26 dam) do significantly more dam.
Keep in mind, MG/Coil/etc all have recoil----ie, more likely to miss if your stats are too low.
Depends on enemies (AR) too. Swords/Kat cut through leather easy, but take more time CB AR (+);
If you have $ or can craft Coil: (assumes = stats!) COIL for heavily AR (CB+) enemies, Kat for everybody else.
Melee in general will save $ in long run (esp in newer ver where we have to pay for mercs Ammo!)
I've used Enya many times (she uses Kat) ----@ hi stats, takes out rifle enemies for a snack! (usually only MG people have CB+)
Stats (again, randomness aside!)
R actually really important. Even w MG/Coil, 2 misses is enough to give an expert ("Heroic?") enemy more than they need. Very few enemies use Kats; But a # use MG or coil;
Like most things, comes down to $; Equipping a 5 person team w Coils (unless somebody drops one!) =$27,500. Does *NOT* include ammo!
Kats R not cheap compared to swordS, (knives, etc) but @ $1500/ea, you could equip a whole team for $7500! (& *YES*,
no ammo needed!)
Finally, Traits: Watch out for "Brawler"; Train best for *MELEE* weapons; There's no similar trait for range weapons.