ONe of the differences between “starting” and “deep cycle”/“Marine” batteries is their internal construction.
Starting batteries have large-area plates to expose as much surface-area to the electrolyte as possible to produce large-current capability for short-periods. Their plates are therefore thinner and more fragile and subject to degradation from vibration and rough use.
That is one reason batteries for rough use such as marine (boats bounce hard in rough seas/waves) tractors, construction equipment, etc. (airplanes too).... those batteries share construction characteristics with “deep cycle” batteries, which have heavier/thicker plates which resist warpage and rough-use movement which can “short” the plates and/or dislodge them from internal connections/bridging. Some of the best rough-use/deep-cycle batteries actually have insulation-materials placed between the plates, submerged in the electrolyte in order to prevent their shorting out against each other as well as to cushion them from vibration. Deep-cycle batteries, with their more robust plates are less likely to warp under deep-discharge conditions and can provide lower discharge rates over longer periods ...but their trade-off is they are not as capable of providing high discharge-rates over short-term periods.
Since tractors, boats, airplanes, etc. typically do not undergo frequent, repetitive starting-cycles... it’s often better to provide them with “deep-cycle” or rough-use/marine batteries.
Buying Tip: If you are comparing batteries to each other of similar types, the less expensive batteries usually weigh less than the expensive ones because they have less plate-material in them. That’s why they also won’t last as long under similar use/conditions.