First off, if you opt for Fi-Core, the Union will no longer recognize you as a member. As mentioned earlier, they say plainly on their website that you will be labeled an FPNM, and they will regard you as an anti-union "scab" (a derogatory term for non-Union workers who fill Union jobs during a strike). Well, the term "fee paying non-member" is technically an oxymoron. How can you pay fees, retain your performer number and be represented by the Union in all collective-bargaining activities and yet be a "non-member"? If you were truly a non-member, you wouldn't be paying dues and you wouldn't be represented by the Union. It would be more accurate to call FC actors "second-class" members, as I said before, but it's their union. They could call you a duck if they wanted to, it doesn't make you a duck.
The SAG-AFTRA website also declares that FC members may not identify themselves as SAG-AFTRA on their resumes, websites, business cards etc. Since Core members are no longer members in good standing, the Union has a right to keep them from using their name to promote themselves. However, they say nothing about simply identifying as "Union: Fi-Core" which lets producers know you are OK to work Union or non-Union projects. I would argue that Fi-Core actors ought to be able to use "SAG-AFTRA: Fi-Core" on their resumes. Adding the designation "Fi-Core" let's potential employers know you are not a full member and it should keep them from being able to do anything legally since you are not misrepresenting your status in any way. However, if you want to be safe and avoid controversy, I've seen a label such as "Union Member: Fi-Core Status" used on a resume along with the actor's performer number as evidence of membership. That seems like a good compromise.
SAG-AFTRA also insists that by going Core, you are hurting other actors in the Union. This statement is pretty much completely true. As we established earlier, Fi-Core does indeed hurt the union by weakening its power in the industry. By extension this hurts full SAG actors because it lessens the Union's effectiveness in contract negotiations. The Guild has had to compete with the recent boom of non-Union projects over the past several years, along with the influx of new digital media. In order to keep low-budget productions from going non-Union, they've had to lower the pay scale for certain film, TV and digital contracts and lower- or even eliminate- residuals on many commercial contracts. So, even the Union jobs on many projects these days don't pay much better than a lot of non-Union gigs thanks- in part, to the growing number of FC actors.
The pro-Fi-Core defense on this point is that this is simply the way it is. Just as certain conditions exist in the workplace that sometimes make unions necessary, likewise, certain conditions exist within unions that make options like Fi-Core equally necessary. Also in a very demonstrable way, SAG itself created the conditions that made the Core option necessary, or at least very attractive, to many actors.
For decades actors have been allowed into the Union with very few prerequisites. All that's required to join is three SAG vouchers from doing extra work on a union set and pay the initiation fee. No training, auditions, evaluations or apprenticeships are required. The result has been a steady stream of new actors with no verified training and no clue how to get work in this business. But the Guild is nonetheless happy to take the ever-increasing initiation fee (currently $3,000) and the bi-annual dues from thousands of new actors every year. And with potentially hundreds of Guild actors vying for any one SAG role, the Union ought not be surprised that people would opt to "hurt their fellow actors" by seeking employment outside the fold.
Maybe you won't worry about hurting SAG's feelings, but you might worry about what people in the industry, who might hire you, think.
Kenzo on IMDb