Visibility and protection
A navigation screen must be readable in sunlight and usable in wet, moving conditions. Check brightness, mounting and weather protection; a regular tablet may need a case and sheltered location.
Charts and connectivity
Check chart formats, licences and offline operation. A tablet can access a local server, but also depends on power and the network providing its data.
Choosing with a backup
Consider size, battery life, updates and installation cost. Test visibility from the helm and carry appropriate alternative navigation resources.
Compare real onboard use
Test visibility from the helm in sunlight and rain, including with polarised glasses, and check whether controls work with wet hands. Dedicated plotters and tablets differ in protection, battery life, mounting and available apps; neither is universally better.
Consider the complete system
Include mounting, protection, power, connectivity and chart costs or licences. If a tablet depends on a local server, test its startup and Wi-Fi coverage too. Before departure, check the route and charts offline and prepare an independent alternative.