Everything you always wanted to know about batteries but were afraid to ask,
courtesy of William Darden.
http://uuhome.de/william.darden/

Huw

It's anologous to
High horsepower or High Fuel Economy.

You can have either, or find a good compromise.
But you can't have a lot of both.

As to exact construction differences, i don't know.
If it's important to you, I can find out.
Texas Parts Guy

Oversimplified enough to be misleading, but I suppose it's not totally
inaccurate.

CCA is the current the battery can deliver for 30 seconds (at 0F and
1.2V/cell). RC is the time the battery can deliver a steady 25A (at
77F and 1.75V/cell).

To build a battery with high CCA, you increase surface area. This
means more and thinner plates, less separation between plates, and
spacer materials that encourage electrolyte diffusion. When such a
battery is discharged, it fails through mechanisms such as plate
breakage and dendrite growth.

To build a battery with high RC, you want plates that will not fail in
discharge, and that means thicker plates, greater separation, and
spacer materials that discourage dendrite formation. Such a battery is
less able to deliver high peak current.

Automotive starter batteries are normally built for high current (thus
high CCA) at the expense of discharge integrity (thus low RC).
Automotive batteries are kept at or near full charge most of the time,
so RC is not usually that important. They will fail quickly in marine
or deep-cycle applications for this reason.

Deep-cycle batteries are normally built for integrity in discharge at
the expense of high current. Thus they make clumsy starter batteries.

Quite simply, cranking capacity is a function of the surface area of the
plates.  If you increase the surface area of the electrode plates, you
decrease the amount of electrolyte that can be contained in the battery,
thus reducing the reserve capacity.

A well designed battery obviously will be an optimization between plate
surface area and volume, and other materials.  This may or may not be
optimized for a particular vehicle.

CCA is determined mostly by the amount of surface area of the plates
while RC depends more on the amount of plate material available to use
up.  So a manufacturer could boost the CCA at the expense of the RC by
switching to thinner plates rather than by making the plates bigger.
Generally, a mechanically larger battery will have a higher RC, and a
larger battery can be fitted in some cars.  But you may have to cut
away part of the battery tray, and keeping the larger battery away
from hot objects or getting the cables to reach could be problems.