Nibenese would be slightly better with magic, diplomacy and bartering while still decent at melee and such.
Colovians would be stronger, taller, more focused on melee and marksmanship, but also fairly good at magic. I wonder what the Colovian special ability would be...Maybe something that doubles armour rating (discipline) for awhile, even going over the armour cap.
Speaking of the Colovians, you may want to hear this
I usually get drawn by a race due to the surrounding lore such as creation myths, history of the race, culture, and overall attitudes towards everyone else. It is so hard to choose one specific race that I always "go to" but I find myself, years after first getting introduced to Elder Scrolls, drawn to Orsimer, Altmer, Redguard, and especially Imperial.
I also tend to put myself into each character I make in some way as I want to RP with the decisions I would make, so Imperial, Redguard, and Breton have been some of my most used races in that order.
During my first playthroughs of Oblivion, I was either an Imperial or Breton. I didn't like any of the non-human races - I found the thought of playing as them uncomfortably weird (for some reason).
Some time much, much later I decided I was sick of playing warrior-type characters and wanted to try something new, namely stealth. In an act of curious experimentation, I decided to be an Argonian for two reasons: first, they had skill buffs and attributes good for the kind of character I wanted to be, and second because they were the only other non-human race I kinda sorta liked.
In time, I discovered that I loved playing the game stealthily. Moreover, my Argonian character started to grow on me. The more I learned about their race's lore, the more and more I liked them. Their portrayal as mysterious, slow to trust and hard to know, appealed to me. I found that while Imperials and Bretons were characters I could relate to in appearance, Argonians I could relate to in personality and temperament.
As a result, my obsession with Argonians has only continued to grow ever since.
Though I still don't like many of the other races, for whatever reason.