Using SAXS and SANS experiments combined with data-driven molecular dynamics simulations, we show that, despite having the same hydrophilic chain and similar molecular weight, these two molecules form drastically different assemblies. Our results highlight the importance of the hydrophobic core in micelle formation and the role of advanced modelling techniques in describing the packing of complex systems. The difference in the shape of the alkyl chain and p-tertoctylphenyl group gives rise to deviation from core-shell structures, with a smooth boundary between the hydrophobic and hydrophilic regions leading to multi-domain structures.