Luck & Power: How the Game Works
First things first, before we get into the game. How does catching a mouse work?
Attraction rate first, because the attraction rate combined with the attraction of the cheese type you’re using determines whether you attract a mouse to your trap at all or not. Your setup doesn’t influence which mouse you attract. If somebody tells you that a certain setup will attract rarer mice because of this and that, that’s either a lie or a superstition. Certain setups can be influential, for instance you will only attract Zurreal the Eternal with Charged Scholar Charms armed and the only effective trap against him is Zurreal’s Folly, but this is one of very few exceptions. Usually you cannot influence which mouse you will attract.
Some people maintain that having a higher attraction rate or higher Luck stats will attract rarer mice. This is nonsense. This is how it works: Brie cheese (for example) has a base attraction of 80%. That means 20 times out of 100 you will fail to attract a mouse (on average, of course). If your trap has an attraction bonus of 10%, that means that 10% out of these 20 times you will cancel out the FTA and attract nontheless. 10% of 20 equals 2. So instead of FTAing 20 times out of 100 on average, you’ll only FTA 18 times out of 100.
Luck & Power
If you attract a mouse, the Luck and Power of your setup determine if you catch it or not. Power is linear, so 2000 Power is twice as effective as 1000 Power. Luck, however, is not. It rises exponentially, so 8 Luck is more than twice as effective as 4 Luck.
It is hard to say what is more important, because depending on the mice and on your setup this may vary greatly.
The rule of thumb is that Power is more important for extremely hard to catch mice, and that Luck helps with the (comparatively) weaker mice. There is a point in the game when Power seems to become more important, which happens around the Duke stage, and is certainly true for the Rift locations. In general, I calculate that 1 Luck equals about 300 power, but this is just a very rough estimate.
Luck & Loot
The Devs have stated that more Luck equals more loot drops. There has been a long and heated discussion about this in the forums already, and I have no idea what the conclusion was in the end, if they’ve even come to one.
The numbers gathered by Horntracker however show that the difference between the usual setups is at best marginal. For this to have a visible effect you would have to have significantly more extra Luck points than you can reasonably get, plus you would have to go on a lot of hunts for it to make a difference.
Conclusion: Luck may boost loot, but the difference is at best marginal. 2 or 5 or even 20 more Luck points won’t make a big difference in loot drops.
Even if more Luck boosts the chances of getting loot, the Devs have also stated that it has absolutely no effect on which kind of loot you get. Especially first timers to the Warpath seem to think that the luckier the setup, the better the chances for a Sandblasted Metal. Sorry folks, that’s not how it works. According to the Devs, you can only enhance your chances of a loot drop, but there’s no way to influence exactly which loot you will get. No amount of Luck, whether it’s 1 or 1000, will help in securing that Metal. There’s simply nothing you can do except leave it to chance. Good luck!
The Effectiveness Meter is an in-game tool that you can find underneath your trap setup by clicking on the word next to “Trap Effectiveness”. It will show you a list of the mice your setup can attract and give you an estimate of how hard these mice are to catch for you. The problem is that this estimate is solely based on your trap’s Power. The Luck part of the equation is not even considered.
The Devs have stated that this is because they don’t want to make the game too easy, plus because there are already fan-made tools which do it. What they’ve failed to see is that because of no warning label or information on how the Effectiveness Meter works, it tends to confuse people. Especially new hunters, who trust it without realizing it’s only partly true.
But the Effectiveness Meter is even more unreliable. In some hunting regions the meter shows you which mice you’re able to attract if you arm a certain type of cheese. In other places it shows you all the mice available in this area, regardless of which cheese type you arm. Keep that in mind when you can’t attract a certain mouse to save your life. It might be because you’re using the wrong type of cheese.
Conclusion: Use the Catch Rate Calculator to check your setup’s ability to catch mice. Don’t ever trust the Effectiveness Meter to give you the whole picture!