Should I go for 300cc moderate plus or 325 high Profile implants? (photos)

Thank you for the question and photograph.  Based on your photograph, I think that you are starting at a great place and should have a very nice outcome with breast augmentation surgery.   
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 are 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 "full C cup”  or "too fake" for example may mean 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. Again, best not to discuss your goals and/or judge the outcome of the procedure performed based on achieving a specific cup size. The use of pre operative computer imaging may be very helpful. 
 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 generally select appropriate breast implant size/profile after the use of temporary intraoperative sizers and viewing the patient's chest in the upright and supine positions.
I hope this ,and the attached link (dedicated to breast augmentation surgery concerns), helps.

Without knowing your exact breast dimensions and a direct examination it is not possible to know precisely which would be best for you. It sounds like your surgeon is in the right range for your appearance, height and weight. Looks like you are quite thin, probably a small B cup, no pregnancies. If you are looking for a full C but "not fake" you will want only modest but not extreme upper fullness (body logic 3/4). Trying a sizer in the office (as you have) can help as well as looking at photographs of "likes" and "dislikes" in similar women to you before and after certain implant sizes.300-350cc range whether moderate plus or high profile seems like a very good choice for you. If you have one more visit planned preop  you can review this all again with your surgeon or again the day of surgery.  He/she will have a range of implants available to make the final decision in surgery possibly with the use of trial sizers to help with the determination.