At first, I made a 2nd character for flower storage. But as I went on, I found so many extra powers I had from having 2 characters:
-2 visits to Katrina each day her tent appears, making it faster to unlock the Fortune telling works project.
-2 visits to Harvey's RV's, getting me more items.
-2 visits to K.K. each Saturday, making it easier to complete my music collection.
-2 requests for furniture by villagers, making it a little easier to customize their home interiors.
-2 Saharah Makeovers for getting more rare wallpapers
-2 Chances at Redd's Gallery, for days he may have 2 genuine artworks.
-A whole new house to expand and create rooms in.
-I get to role play as my second villager, and have fun being a different personality with my villagers and other players.
-An opportunity to get an extra set of rare items, such as Golden Tools, Post Office awards (piggy bank, etc.), Game console awards, etc.
-Extra Path Patterns (Although I never needed them).
-A way to trick the game into spawning more Jacob's Ladders, simply by having the second character 'hide' the ones you got in their storage, and your mayor character always the one to start up the game each day.
There's probably even more to get from having a second character, but there indeed are lots of great uses for them!