You would never use one over a FF card if you have one that fits your team. Stats, awakenings, etc, are all better as they always are with REM cards. How effective they will be depends on the team you put them on. They all have low attack, but assuming they can accept relevant killers and the team can burst hard enough in general, they will do their job. For people who didn't get the pixel they wanted in FF, they may be an option depending on the team they are going to be used on. If you triple latent killer a card, and make the 3x3 box, that card has an additional ~8.5x multiplier. With a good burst, a huge attack stat won't be needed. Now, who knows what future dungeons will be like such as Alt. Arena. Might be way too low, but for what we have now, don't see them being too terrible if you choose to invest in one.