I married Ysolda with my first character. Best thing about her is she became a merchant, giving me an extra outlet for all the junk I picked up adventuring. I haven't tried marriage for my current character yet, so I can't say more than that. (Oops, just looked it up, and all spouses become merchants. Dang. I thought that was something special for mercantile-type spouses, and that magic or combat-based spouses might offer something different. This needs a mod!)
The only character I felt any desire to marry my own character to was Angi, who can not be married. I think I will correct that when the CK comes out.
Who is best suited to your own play style depends, a follower can still be recruited when married, a merchant still sells goods. Personality wise, that is dependant on your own taste.
Since it sounds like you're on PC anyway, why don't you go into the console, click on her, and enter the command:
addfac 19809 0
This should let you marry her. I think. (Haven't tested it myself.)