If you are looking for the maximum cranking amps in the smallest battery likely AGM is what you need.. I have held in my hand an AGM battery that was on the order of 30 amp hours (By comparison a common Group 24 is about 73 AH at the C/20 rate) This little battery was capable of 1,000 cranking amps. Just not for long.
So I'd say if it's cranking amps you want go AGM.
HOWEVER:
The problem with 12 volt batteries is they come in many shapes and sizes, From small ones that fit in the palm of my hand and run things like hand held spot lights or your kid's electric barbie car. (Remember when the kids had to pedal those little rides, now they are electric, LAZY).
to.. Well once I was Field Day chair for our ham radio club.. I made the decision to go battery op (Got 1st in the state we did, good decision). Next to the hospital where my wife worked used to be a battery rebuilder.. They moved from Redford to Novi, MI. I went out and borrowed one of their batteries.. They strapped it to a pallet and loaded it onto the U-Haul trailer I'd rented...... With a fork lift... Powered by a twin of the battery they loaded... I would guess that was close to a ton of lead (And that is NOT, in this case, a figure of speech)... And it is also NOT the largest battery in the plant.
