I would frame this as safe mainstream ownership versus distinctive value. The Galaxy S26 FE is likely to appeal more if you value Samsung’s ecosystem, service network, resale familiarity and a conventional camera/software experience. Nothing Phone (3) is more interesting if you like its design language and software approach and the local price is clearly better.
Compare camera consistency rather than sensor counts, especially indoor photos, motion and video. For performance, look at sustained behavior and heat. For long-term ownership, check the remaining update policy and local warranty support.
If prices are close, the safer ecosystem choice may be worth it. If Nothing is substantially cheaper while meeting your camera and support needs, that price gap can make it the smarter value buy.