Final answer:
Homo rudolfensis likely had a larger brain than Homo habilis, but robustness is harder to determine due to limited fossil evidence. Both exhibited traits significant in the classification of the genus Homo.
Step-by-step explanation:
Between Homo habilis and Homo rudolfensis, evidence and fossil records suggest that H. rudolfensis had a larger brain size. While H. habilis had a brain volume of about 550-690 cubic centimeters, H. rudolfensis is estimated to have had a slightly larger brain, based on cranial measurements. However, due to limited fossil evidence, particularly the lack of postcranial remains, the robustness comparison is less clear.
Some propose that H. rudolfensis might be a more robust H. habilis male. Moreover, since tool use and encephalization are strong indicators in classifying species in the genus Homo, H. habilis with its smaller teeth and more advanced hand structure for making tools, provides evidence of these human-like traits.