Well, here's what I see, when I plug these two into Rebal's current iteration for weapon balance. You can compare the current Rebal versions with the Vanilla ones
here, if you're interested in reviewing the current methodology.
So, comparing the two Vanilla weapons, the current Light Needler is substantially worse in almost all ways.
Why? Two things: accuracy and Armor penetration; but mainly it's accuracy, because one exacerbates the other. The Light Needler's accuracy at 700 is actually fairly poor, missing the target 20% of the time, on average, vs. the Railgun's more-than-perfect accuracy (101%). It's actually a little worse than that, because I don't fully calculate the random stat when it stacks per shot; by the time the Light Needler's 6th shot is out, it's already hitting less than 100%, and it goes downhill fast; the last shots are less than 50%. Nobody really notices this much in-game, where it's a flurry of shots, but trust me, that matters, against small targets.
And that's a lot of what people are complaining about, in terms of practical effects, too.
The Light Needler is, if we ignore the accuracy problems, a more Flux-efficient shield-crusher; it fires 15 shots for 750X2 = 1500 Hard Flux per burst, with a relatively-decent Flux efficiency of 0.8 for raw DPS. So, vs. large stuff that can't dodge, it'd be great for Flux-locking.
However, the Railgun will actually
hit the same places over and over again, whereas the Light Needler's going to spatter the target with its needles. And when the Railgun hits, it's doing twice the damage vs. Armor (granted, that's a paltry 50, even before Armor calcs start whittling it down, but still, it's not a total joke).
So, against Armor, the Light Needler will be considerably worse. Against Hull exposed in only a narrow hole, it'll be worse. Against something stripped of Armor, it'll be better, but only a bit.
This is why it feels "weak" now; without the huge range advantage it enjoyed, making it the best-for-cost kiting gun, it's not great.
Anyhow, that's basically what's going on here; it's pretty cool to see what I've been saying be so accurately reflected in player comments.
So... fixes that stay in-theme? The last set in the sheet reflects my call there. Light Needler gets more DPS and is obviously more efficient per shot... but stays spray-and-pray and is still lousy at killing Armor. The Railgun is slightly less efficient, but ever-so-slightly positive. Both weapons get their big shot-speed differentials set to 1.0, but the Railgun could trade a little less efficiency for really fast shots easily enough, to make it the super-accurate steady-hitter it's supposed to be.