Tubular vs flat plate
Tubular and flat plate describe the positive plate construction inside a lead-acid battery.
Flat plate batteries
Flat plate batteries have pasted positive plates. They are generally cheaper and accept charge quickly, but typically have a shorter life in deep-discharge backup use.
Tubular batteries
Tubular batteries use a tubular positive plate with the active material held in tubes (gauntlets) around a spine. This construction generally gives longer life and better deep-discharge performance, which is why tubular batteries are the common choice for home inverter backup.
Which to choose
If your area has long or frequent power cuts that discharge the battery deeply, a tubular battery is usually the better fit. If cuts are short and the battery is rarely deeply discharged, a flat plate battery can be adequate at a lower price.
Confirm the exact warranty terms (full replacement months and pro-rata months) before buying — these are the figures that tell you what the manufacturer actually guarantees.