Is 750ccs in each butt cheek (BBL) enough to have a noticeable difference? (Photos)

Patients interested in BBL often ask questions of the necessary volume for transfer. Ultimately, the answer is two pronged and based upon both patient expectations and the nature of fat graft themselves.
BBL and fat transfer is ultimately dependent upon the long term viability of the fat grafted. That being said the resorption rates of fat transferred can be significant. Clinically this translates to a progressive loss of grafted volume in the months following the procedure.
I tell patients that they can expect resorption or graft loss on the order of 50% (at most; prepare for the worst and hope for significantly better). Additionally some harvest volume is lost in processing the fat graft prior to transfer. Thus I generally recommend that patients seeking even the most minimal volume increase have adequate reserves for grafting of 500 cc per cheek (at minimum).  This means that harvest will usually exceed 1 liter (assuming for processing loss).
However, it important to remember that these are recommendations and can be amended based upon a patient's particular expectations. Some patients only want a subtle change and may be willing to accept a less significant result. But the rule still applies you have to have the fat to transfer the fat.
Based on your photos/goals, you appear to have adequate reserves for a modest augmentation. 750 cc per cheek (after processing losses etc.) should provide a long term increase of around 350-400 cc once healed and stabilized (following resorption volume losses)
As always, discuss your concerns with a board certified plastic surgeon (ABPS). 

Thank you for question and the photos. It is very difficult to give a specific number looking at photos, and the amount on its own it not very important. It is important that the surgeon tries to give you the desired results that you are looking with the material that he has available , if realistic. Best of luck