What is a WHr (watthour)?

It depends on the draw of the laptop, so the laptop, peripherals and how you use the laptop come into play.

For example, with the 62WHr battery if the laptop draws about 12.4 watts, then the battery will last 5 hours.

The 43WHr battery at the same 12.4 watts will last about 3.5 hours. But if its a low consumption device it could last the same.

The correct symbol for it is Wh

1 Wh = 1 Watt * 1 hour = 1 J/s * 3600 s = 3600 J

That's the energy stored in the battery, which is completely not related to time. The larger the number, the more energy it supplies. 1Wh means if a device's power is 1W, it can last for 1 hour with that energy.

However usage time depends on the power consumption, not energy. On the same energy level, the higher the power, the shorter the battery lasts. Every computer has different power requirements so the time varies. The power isn't even fixed during runtime but varies depending on the CPU load and peripheral devices usage.

For example a laptop that has an average power of about 20W uses a 60Wh battery will have 60Wh/20W = 3h of life time. But another 15W laptop can run on the same battery for 4 hours.

As an electrical engineer specializing in technology and automation; Unfortunately the answers above are about as close as you are going to get without more technical data on the system, peripherals, and typical usage stats.

The higher the mAh/WHr within the same system with the exact same hardware and the exact same usage paterns; the longer you can stay powered between charges. Just as with cell phones, idle time vs on the web vs on a game vs on an actual phone call... wifi vs cell sygnal, signal strength... all these things affect power consumption on a cell phone, and many of the same factors will affect the "battery life" on any computer, and yes even the most simple cellular phone is a computer, smart phones are just more advanced than the simpler ones.

P.S. screen size, brightness settings, sound/volume also play into battery consumption. I would suggest carrying a back-up battery pack, again, the higher the mAh number the longer the additional time permitted with this device plugged into you equipment. Dell offers a 12000 mAh pack that is compatible with many of their laptops, I am not sure of other manufacturers.