What are the quality and popularity of Nagor implants?

Nagor implants are NOT distributed in North America.  They are produced in the UK and are not approved for use in the Unites States.

Both Nagor, an implant manufactured in the UK, and Silimed are implants that not approved for use in the United States. As Dr. Grzeskiewicz mentions Sientra is an implant that is a subsidiary of the Silimed but these are not the same implants. If the surgery is being performed in the United States, you should consult in person other board certified plastic surgeons to understand your options.   

Unless you are having surgery outside the US, your surgeon should not have access to Nagor, nor should he or she be recommending them here.  They may be a fine implant, but they are not approved for use by the FDA.  In addition, Silimed implants aren't either - Sientra, the US subsidiary of Silimed, does have approval to sell implants here, but that is different because each of the companies approved in the US sells a different version of their implants abroad too.  Check your facts with your surgeon if he or she is US-based, and if not, you'll have to rely on opinions from surgeons outside the US on the Nagor implants.

Nagor implants are manufactured in U.K., while
Silimed implants are from Brazil.Although both manufacturers claim safety and high quality, these brands
are not U.S. FDA approved, so be cautious if a surgeon will be using either of
the implants and the procedure will be done in the States. You might have a
problem later on.

Your information says you are in Maryland. If this is true, then you should not work with the surgeon who uses these brands as neither are approved for use in the US. The only brands approved are Allergan, Mentor and Sientra. I have never found a problem in choosing an implant from any of these although I prefer Allergan and Sientra textured implants