I want to downsize my breast implant. Would 50 or 75 cc make much of a difference? (Photo)

It has only been three months since your breast implant surgery was done. You still have some swelling, so I recommend that you wait another three or four months to see how you like them when all of the postoperative swelling has subsided, an d your tissues have relaxed.
To answer your question directly, 75 mL would make a noticeable difference, but it would not be worth the extra surgery to reduce by 50 mL in my opinion. It generally takes from 25 to 40 mL to even tell a difference.
Thank you for your question and photographs, and good luck.

Going down 75 cc would make a subtle difference, probably less than 1/2 cup size.  But I would recommend waiting until you are at least 6 months and maybe even a year after your surgery.  Your perception and happiness with your size may change over time.  Fortunately, if you do decide to switch implants it is a easy procedure to have done.  Good luck.

You
state that your breasts make look heavy. 
That is because your breasts are too low and augmented.  The preferred technique for you would have
been a breast lift.  Women hate breast
lifts because of the vertical scars associated with the traditional
technique.  I recommend explantation using
The Bellesoma Method.  Your breast tissue
is reshaped creating upper pole fullness without implants, elevated higher on
the chest wall and more medial to increase your cleavage.  Vertical scars are avoided, nipple sensation
and the ability to breast feed are maintained, if not injured from your
previous surgery.  At the same time or
later, fat transfers can be performed if additional volume is desired.Best Wishes,Gary Horndeski, M.D.