I think that ACRO and Barrons suck (honestly). Cliff's is too easy on the bio section, and too hard on the chem section. But the verbal and reading sections are just about right. Kaplan has good bio, chem, and reading section, but it has hard sentence completion questions (the analogies are okay). Regarding the math, use kaplan. I would recommend you using a combination of cliff and kaplan for your best guide