Will there be a noticeable difference between 275cc and 300cc high profile round implants?

Choosing an implant size/style is an important decision which is best made in concert with your surgeon. Ultimately, options are based on a number of factors including:
-Chest dimensions: This point is crucial as the width of your breasts defines the available "real estate" on which the foundation of your augmentation is built. This "foot print" is the absolute limit with which you are dealing. Too "large" is not so much the risk as too "wide." You cannot build a 3 acre mansion on a half acre plot. An implant which is too wide (exceeding the available space on your chest) will generally over hang laterally making it more noticeable and occasionally contributing to discomfort and nerve symptoms (numbness or tingling). This will also contribute to a more unnatural look.
-Tissue quality: This relates to size in the sense that the implant will be suspended by your tissue. Too large an implant may place took large a stress on these suspending tissues leading to healing problems in the short term and bottoming out in the long term.
-Patient desire (what is the look you are hoping to achieve?)
My role as a surgeon is to manage expectations and guide you towards a prudent choice which can satisfy these reasonable goals. Often times, a surgeon can guide a patient toward a size/cc range and patients will make determinations on implant style/profile. Patient seeking more or less projection, or seeking a more pronounced or subtle upper pole volume increase can be guided toward an implant which will help them best achieve their goals. Additionally, technique variations (sub muscular vs. sub glandular) can also aid in obtaining the look you desire.
There are a number of tools available to help guide patient/surgeon decision making including sizers, 3D imaging and goal photos. Each modality can help better communicate your goals to your surgeon and vice versa.
Ultimately, it is important to not marry oneself to a particular "cc" as oppose to a particular "look." Communication is key as you and your surgeon create your custom surgical plan.
With regards to your particular question, 25 ml is a very small volume differential (45 ml approximates a shot glass). Most will not be able to distinguish between the 2. I will typically order flanking sizes so patients can makes last minute adjustments that are still within the ballpark of their chosen implant.
As always, discuss your concerns with a board certified plastic surgeon.

Hello, in short there will not be much of a noticeable difference between the two sizes. The difference will be in the diameter of the implant. 25cc in volume is similar to about half of a shot glass. Depending on your breast width one might fill your width more than the other. A good question to ask yourself is "would you be upset if you woke from surgery and were slightly smaller than you expected or slightly larger than expected"? Your answer to that question could help you decide on the size since there is such a small noticeable difference between the two sizes.

The simplest answer to your question is that a 25 cc difference is less than 2 tablespoons. This is usually very difficult to detect visually. Depending on your wishes and expectations, you would probably need a larger volume to notice much of a change. Good luck with your surgery.