Cisco's IOS maintains the same look and feel across the entire router family of products. Unfortunately, I can't say the same for the entire switch family of products. However, it is a Cisco goal for that to occur one day. The reason for the two main command sets of the switches is basically evolutionary, partly Cisco and partly their acquisition of products with a good installed base. Some of these products are listed here:
Grand Junction 1900 and 2800 switches use a main menu display where you select a letter.
Kalpana 3000 series switches have you move through menus by highlighting an option using the arrow keys and pressing Enter rather than a letter (like the Grand Junction products).
Crescendo 2900 and 5000 series introduced ...