There is nothing/not much/little to choose between A and B
Definition 1 of 1
Pro Tip 1/3Decision Difficulty
Use when choices are so similar it's hard to decide; often for options of equal worth. 
With their identical features, there's little to choose between these two smartphones.
Pro Tip 2/3Nuanced Differences
Implies differences exist but are so subtle they might not influence the decision. 
There's not much to choose between the two routes; both get you there on time.
Pro Tip 3/3Equality Emphasis
Stresses equality in quality or value, not always physical similarity. 
Both are top students, so there's little to choose between them for the scholarship.