Depending on your starting height; I would say that another advantage of going femurs (other than safety and capacity to lengthen) would be that you can wear some fashionable height increasing shoes (1" to 3" additional height and it will balance out your proportions nicely since this will elongate your tibia appearance there by complimenting your increase femur length. If you do go Tibia's, then that may compromise the amount of lift you can wear post lengthening without appearing a bit long below the knee.
Now with that said; if you do not plan on increasing height with shoes at all after CLL; then I would say that tibias are probably less noticeable. Keep in mind that a 2" to 3" increase on either bone will not be a notable difference for most bodies.
Answering your question directly however. I have a sense that the increased tibias may show off a taller appearance since they are more apparent with shorts and when bending knee in pants. Additonally, although the femur is the "largest" bone in the body (I do believe); to me at least, I have always had a visual sense that the below the knee proportion of the leg always appeared longer. I'd like to learn about what other opinions are regarding this topic!