Here are are some pros and cons of lengthening a particular segment. Evaluate these options and decide accordingly.
Femur Lengthening:
Pros:
1)Faster healing and recovery. Since Femur is muscular and has better blood supply than tibia, it has higher rate of healing. I've see few cases where the person had performed bilateral lengthening and was still be able to return back to normal life in as less as 4-5 months.
2)You can still wear shoes with thick sole and look aesthetically good.
3)No risk of permanent Knee pain when the nail in inserted through hip.
4)You can still wear shorts without exposing your scars.
5)You can achieve greater lengthening amounts as compared to tibia. As in - recommended safe amount in Tibia is 6 cm, but femur it goes up to 7-8 cm.
Cons:
1)Aesthetically, you may look stocky but not tall. You've already mentioned that your femur is already quite longer than tibia, so your proportions are going to get deteriorated a bit.
2)Expensive, as internal nailing is the preferred approach for Femur lengthening.
3)Knee bending and decreased range of motion in knees. This is known to be eliminated by IT Band release without any reported side effects as of now.
Tibia Lengthening:
Pros:
1)Aesthetically, you would look taller.
2)Less expensive, when you choose LON or External method.
Cons:
1)You may not be able to wear shoes with thick soles, as it would make your lower legs look disproportionately longer (may be not if you did 5 cm).
2)Risk of permanent Knee pain if you go with internal nailing technique. This was one of the major factor why I went with totally external technique. One suggestion I would give for LL'ers is not to gamble with risks that can cause long term suffering. My golden rule was to sacrifice short term inconvenience for long term safety and convenience.
3)Not advisable to push for beyond 6 cm.
4)Risk of ballerina when you lengthen excessive amounts, where you would end up walking on toes. This can be avoided by performing Achilles Tendon Lengthening (ATL) or Gastrocnemius Recession. However, these procedures are infamous for greatly reducing your leg strength, and therefore strictly not recommended.
5)If you have bow legs or curvy legs or knock knees, internal method is not possible. You would have to opt for external technique, where you would end up in frames for almost 1 year depending on the amount you lengthen.
Keep in mind that everyone is different, and above bullet points may or may not apply to you. However, you can use them as a guideline for making a decision. Age also plays a vital factor. The younger you are, the faster and better are your chances of recovery.
All the best!