I have both the Ivette and the Lang. I’m not someone who typically wears heels/stilettos, so take this with a grain of salt.
I thought the Lang looked beautiful both on the foot and in terms of height/proportion, as the straps laid on the foot nicer. The Ivette is a beautiful shoe, but I think when they made the shoe shorter, the straps tend to gape out a bit. In terms of comfort, the Ivette was much more comfortable for me due to the shorter height. I actually wore these on my wedding day through hours of pictures and dancing. The Lang I can’t wear for more than 15 minutes of standing/walking without having to sit. However, my salesperson who recommended them to me told me she’s perfectly comfortable in wearing them for hours. She seems to be much more accustomed to wearing high heels though!