The_root_of_all_evil said:
Lasers by far.
1) Speed: Light versus Sound. No contest.
2) Penetration: Heat vs Kinetic. No contest. Especially as heat is recurring damage.
3) Range: LOS vs Gravity: No contest
4) Utility: Try turning a Railgun down.
5) Adaptability: Try firing a Railgun underwater.
6) Energy: Total Energy Conversion versus Air pressure. No contest.
7) Ammunition: Closer, but light is still more prevalent.
8) Reliability: One tiny problem in your magazine and boom.
9) Weight/Recoil: Easy win for lasers.
10) Stealth: [sub]zit[/sub] versus BOOM. No contest.
Seriously, the ONLY thing Railguns have in their favour is blowback.
I know this is a bit late, but it wouldn't stop bothering me. http://imgs.xkcd.com/comics/duty_calls.png
1) Speed: In this case you are half-right. Nothing can beat the speed of light, however the speed of a railgun's projectile FAR exceeds the speed of sound (a railgun shoots at 11,500 feet per second or approximately Mach 10.) In relation to guns today, they don't need to be any faster aside from power.
2) Penetration: Not much of today's armor (or probably that of the future) could stop an impact with that much force. Also, if you know much about guns and entry/exit wounds generally, you know what kind of damage this means.
3) Range: LOS is actually worse than gravity in Earth's conditions as lasers couldn't be fired like the artillery of today which impact beyond the horizon. In space conditions, I go to Newton's first law.
4) Utility: As far as weapons are concerned, why would you want to turn down the power of a railgun? I acknowledge lasers could be turned down to cauterize wounds, but I doubt they would use a weaponized laser for that purpose
5) Adaptability: A laser would lose most if not all of its heat energy vaporizing the water near the beam (much like how it would lose energy to the intended target), though a railgun wouldn't do much better underwater functionally.
6) Energy: Railguns aren't conventional weapons and don't rely on air pressure or gunpowder to shoot the projectile. (Magnets, how do they work?) Railguns would use much less energy to propel a greater destructive force.
7) Ammunition: No problem really, ammunition would essentially be loads of metallic weight.
8) Reliability: There are no explosive charges in railgun ammo, only when they hit you do they go boom. Speaking of a boom, kinetic energy itself can be great enough to cause an explosion (big enough to be like that of a nuclear weapon,) doing more damage over an area than a laser.
9) Weight/Recoil: The energy required for either railguns or lasers would require a power plant to work how they do in sci-fi (Halo specifically). You wouldn't need to worry about weight or recoil when mounted on the ground. In space, you have to compensate for equal and opposite reactions, however weight would not be a problem.
10) Stealth: There is no air in space to transfer sound, and there isn't much stealthy about light bright enough to melt steel.
We're also much closer today to developing railgun technology than we are lasers.
