To be precise, 15-inch laptops typically equip 15.6-inch displays, which are considerably larger than 14-inch displays and provide quite a bit more room to work. That also makes 15-inch laptops themselves significantly larger, even given today’s minimal display bezels, which is one tradeoff. Another is that the larger the display, the less sharp it will be at a given resolution. So, while Full HD (1,920 x 1,080) might be fine at 14 inches, it can be less sharp than you want at 15.6 inches. You’ll want at least QHD (2,560 x 1,440) resolution to ensure that text and images remain sharp. Another tradeoff is in battery life, where the larger the display, the less longevity — which is why 15-inch laptops tend to have larger batteries, which contributes to their usually heavier weight.
So, the question of whether you should buy a 14-inch or a 15-inch laptop comes down to how you feel about those tradeoffs and how important the increased screen real estate is to your workflow. If you tend to open a lot of windows and keep them side by side, then you’ll benefit from a 15-inch laptop. If you tend to single-task, then a 14-inch laptop might provide a good compromise between chassis size and weight, screen size, and resolution.
In many ways, a 15.6 inch laptop, with a separate numeric keypad, hold advantages over their smaller counterparts.People who work extensively on documents, slides and spreadsheets, and also some design and graphic work, need to use arrow keys. While the arrow keys in a 15.6 inch laptop are big, they are smaller in their 14 inch counterparts. Small arrow keys in a 14 inch laptop can be a hindrance when users want to navigate quickly.
15.6 inches would offer you better interface where your eyes don’t have to strain while reading ,watching or conducting any kind of work on your laptop.
On the other hand 14inch laptops are more portable and usually have less weight.
If you travel a lot and have to take your laptop everywhere, get a 14 inch one. If you don’t have so much of travelling and just sit on a desk to do your work, a 15.6 inch would be good.