Although both are practice tools, their roles are slightly different.
A RRB JE Sample Paper is best for concept reinforcement and regular practice. It helps you stay in touch with the syllabus and improve consistency across subjects.
A RRB JE Previous Year Question Paper, on the other hand, is best for understanding exam trends and real difficulty level. It shows you how questions are framed in the actual exam and what level of depth is expected.
Using both together gives you a complete preparation experience—one builds skill, the other builds accuracy and confidence.