Since you love the size of the City I would go for the City again... its always nice to have 2 bags that are the "perfect size" for you... Maybe get a First as a 3rd BBag in a nice bright color for nights out!
City since its a perfect size for u. First is a bit small IMO. Possible to exchange for a city if u opt for first and regretted it??? Mandarin first is also another nice pop color to consider. Let us know what's yr decision Good luck.
Honestly although Sanguine is a gorgeous color (I LOVE MINE TO DEATH) but its not Bright enough to pop but instead is a very "Neutral" color in a way as it goes with EVERYTHING.
So I suggest a Sanguine City as you will use it ALOT (trust me ). Since its the perfect size. For First I would suggest a really BRIGHT or pale color (for possible color issues ) as you most probably will use it for errands or night out. Nevertheless, SANGUINE IS TDF!!! Go get it already!