What's the difference? Is the gain on ceramic bigger or not?
PS: I don't know what to say, but I only ask for those pickups difference in general.
This may not help a lot, but here is one person's opinion + facts about magnetic cores: sonicwrench forum
Q: What is the difference between Alnico and ceramic magnets?
A: Alnico magnets are made of an alloy of Aluminum, Nickel, and Cobalt. Ceramic magnets are made from ferrites (often iron oxides). Magnetically speaking, ceramic magnets produce a stronger field than Alnico. The result is a slightly hotter sounding pickup with more treble response. A lot of people automatically say that Alnico is superior to ceramic in pickups. Alnico tends to produce a very musical pickup in most setups. However, there are fantastic sounding ceramic pickups out there (such as the G&L “MFD” pickups), as well as our own humbuckers and P90′s. The reason ceramic has a bad rap is probably due to its use on low quality instruments, in low quality pickups. Ceramic magnets are often useful in high-output pickups to help retain high end that is lost due to overwinding, and help to create crunchy sounding pickups for hard rock, heavy blues, and metal styles.
So like a lot of components in musical instruments, which is "better" depends on what you want for sound output.
Ceramic magnets do produce a stronger field, but that alone doesn't actually change the sound, it just increases the total output (which, of course, will change the sound if you thereby drive an amp further into distortion).
What's more relevant is that Alnico is magnetically "softer" (It has a higher reversible permeability) than ceramics, i.e. it changes its field more when affected by the string's movement. This effect is not very strong, but it notably influences the pickup's electrodynamics: the inductance becomes bigger, as a result the resonance frequency is lowered. Also, Alnico is an electrical conductor; this will "drain away" some of the resonance.
All these effects together cause Alnico pickups to sound somewhat warmer, gentler than ceramic-magnet pickups; however other factors such as winding number are of cause also important – it's not really possible to say "that's an Alnico sound".
This is what I found in one study made by Oak Ridge National Laboratory under US Department of Energy:
Ferrites contain mixed domains, some in opposition to the magnetization, therefore a weaker magnet
Alnico has high remanence but low coercivity. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses).
This makes Alnico to be a better magnetic core than Ceramic (Ferrites).
I have four electric guitars. Two have ceramic pickups (G&L F100, 1982) and an Ibanez clone built in New Hampshire. I have a PRS SE (Korean) 22 fret model and a 2002 Squire Standard Telecaster that have alnico pickups. Only the Squire has a fixed bridge. I love alnico because of the sound. I can only describe it as sweeter. The G&L mentioned above is a fantastic guitar in regards to build quality and I do understand how it is good for major distortion but at the same time alnico works for me too. To put things into perspective, I am a distortion and sustain freak but not a modern metal person. It is very difficult to compare the two magnets (or individual replacement pickups in general) unless you are prepared to spend a great deal of time and money trying them out in the same guitar. What is really weird is I cannot tell the difference unless I am the one playing the guitar, for what it's worth.