Rising fertilizer costs, nutrient-use inefficiency in conventional agriculture, and the environmental burden of synthetic nitrogen and phosphorus have driven sustained research interest in two distinct but often conflated technologies: biofertilizers, which use living microorganisms to enhance nutrient availability and uptake, and nano-fertilizers, which use nanoscale formulations to improve nutrient delivery efficiency. This review synthesizes peer-reviewed meta-analyses and field trials (2017-2026) evaluating both technologies' agronomic potential and documented limitations. Biofertilizers — including plant growth-promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF), nitrogen-fixing bacteria, and phosphate solubilizers — show consistent, well-replicated yield benefits of 8-20% across climates in a 171-study global meta-analysis, with substantially larger biomass and nutrient-uptake benefits (up to 100%+) under drought stress or in mycorrhizal associations, and their efficacy is strongly moderated by soil phosphorus status, climate, and choice of microbial strain. Nano-fertilizers present a more contested evidence base: a landmark meta-analysis of 78 studies found a median 20-30% efficacy gain over conventional analogues, and numerous promotional field trials report large yield and nutrient-use-efficiency gains for nano-urea and nano-zinc formulations, yet an independent, peer-reviewed two-year field trial found nano-urea substitution for conventional nitrogen produced significant yield penalties (13-21.6%) and reduced grain protein content in rice and wheat, directly contradicting manufacturer claims. We conclude that biofertilizers represent a mature, context-dependent but scientifically well-supported technology best suited to phosphorus-limited, dry, or drought-prone systems, while nano-fertilizers remain a promising but still unsettled technology whose real-world performance, environmental safety, and appropriate use protocols require substantially more independent, field-scale verification before they can be recommended as a substitute — rather than a closely monitored supplement — to conventional fertilization.