Hello candidate..

To answer this question, I am assuming that this question has been asked with regard to Medical Biochemistry, as these two books are standard textbooks for 1st year in Medical School.

Biochemistry can be roughly divided into 3 major sections:

1. General Biochemistry of Carbohydrates, Proteins and Fats
2. Metabolism of Carbohydrates, Proteins and Fats
3. Molecular Biochemistry comprising Genetics

For section 1 and 2, I prefer Harper. Metabolism portion is explained vert lucidly in Harper. Lippincott has good illustrations, but the text in Harper is better.

However, for section 3, the text in Harper isn't very lucid, and It lacks good illustrations. So, for this section Lippincott’s Biochemistry came to my rescue.

Medical Science is an integrative science. No single text book is enough to clear all doubts and build all concepts. One has to refer to different books.

In addition to Harper and Lippincott, I'd suggest that you look into Lehninger and Genes X (for genetics). You don't need to study these two books thoroughly as that is beyond the requirement for exam, but you may however refer to these for getting some doubts cleared. I did the same.

I hope this answer helps!

Regards!