Okay, I asked... He said it's pretty complicated, but there is very little difference between alnico magnets or ceramic magnets as far as what you can hear. Why? Because of flux density changes in the coil (and coil sizes differ). Heat affects the sound, too - especially on ceramic magnets. Alnico - heat doesn't affect the sound as much.
The big deal is the cab. Open back, or closed back? Speakers mounted side by side, one above the other, or at an angle makes a lot of difference. Feet on the bottom of the cab, or no feet? Wheels? Cabinet material and speaker mounting on the baffleboard (front or rear), affects the sound.
One thing that has no affect? Speaker companies make all this noise about using oxygen free copper wires in such and such a weave - it's all bull****.
He suggested you watch a bunch of Johan Segeborn videos where he compares speakers - like 12 or 16, one at a time. Very informative stuff. Good luck!
OK thanks for that. I had a look at the famous Celestion Alnico blue, 12" . The magnet is quite deep on that , the cone is deep. It's rated at 15 watts which seems low. Quite expensive to buy. The other thing is they weigh some 9.3 pounds. Quite a weight for a speaker, but people seem to love the effect on the sound of an amp