For larger lawns, the Cobra 40V 51cm is the better choice, though the Lawnmaster 48V has slightly more raw motor power.

Here is why:

Cobra 51cm (Better for Scale): The 51cm cutting width is significantly wider than the Lawnmaster’s 46cm. On a large lawn, this extra width means fewer passes and a much faster finish. It is built specifically to handle bigger areas efficiently.

Lawnmaster 48V (Better for Torque): The 48V system (usually 2 x 24V batteries) provides more "grunt" or torque. This makes it slightly more powerful for cutting through very thick, damp, or neglected grass without the motor bogging down.

Verdict: If your lawn is well-maintained but large, get the Cobra 51cm to save time. If your lawn is rough, thick, or prone to overgrowing, the Lawnmaster 48V is the more "powerful" workhorse for tough conditions.