Dell have different models and the Vostro line comes with decent design with reasonably good build quality and most importantly it is aimed at the price conscious buyers. Here in this page we compared the two Dell Vostro models which has the same internal hardware specifications. The only major difference is the size of the display. On the Dell Vostro 2420 the screen size is 14 inches whereas on the Dell Vostro 2520, the screen size is 15.6 inches.
You could find on most of the laptop models the difference between a 14 inch disply and a 15.6 inch display will be the display size and the keyboard. The 15.6inch displayed laptop generally comes with a dedicated numeric keys on the keyboard. But, in this Dell Vostro 2520, there is no difference in the key layout. It is almost same between the 2420 and 2520 models.
The connectivity options on both the models also same. Both these 2420 and 2520 models have the following connectivity options and ports in common.
Take a look at the images of Dell Vostro 2420 and Dell Vostro 2520 for a visual comparison.