500cc or 550cc for 5´6" and 119lbs?

The photo's that you have shown are not cohesive with the wishes that you are expressing.  The pictures are showing a much bigger image than the bra size that you say you would like to be.  I happen to believe that a high profile silicone implant gives an unnatural look.  If you are looking for a more natural look I would recommend the moderate plus gel implant. 

In my office, we use an implant sizing kit which has helped our patients choose their size with much higher satisfaction rates. Essentially, we take your current measurements to determine what implant sizes work well for your body. This usually gives a range of +/- 300cc. Then, the implant sizing system is used within your own bra to give a very good idea of what different size implants do for your overall body. The Mentor sizing kit is an excellent way to show you how you would look with different sized implants in real life - no computer imaging or rice bags needed. This allows you to focus more on the outcome of a size rather than the number of "cc's".

Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you're looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon. This communication will be critical in determining  breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as   “natural”  or "too big" or “C or D cup”  etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate. The use of computer imaging may be helpful during this communication process.
3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery.
I hope this (and the attached link) help. 

It is common for a patient to express which size they would like to be and then the picture they want to look like is something different. The girls in the pictures you have attached are clearly DD bra size or more. You are expressing that you want to be a small D. Although you can probably accomodate an implant that big, keep in mind that because of your small frame they will not have a natural appearance and will most likely end up being a DD cup size. I would recommend a smaller implant if you want to be a small D.