Atorvastatin’s improvement in efficacy over simvastatin is slight. I wouldn’t pay much more for it.
A comparison of atorvastatin, pravastatin and simvastatin, based on their effectiveness against placebos, found that, at commonly prescribed doses, there are no statistically significant differences among agents in reducing cardiovascular morbidity and mortality.[14]^ Zhou Z, Rahme E, Pilote L (2006). “Are statins created equal? Evidence from randomized trials of pravastatin, simvastatin, and atorvastatin for cardiovascular disease prevention”. Am. Heart J. 151 (2): 273–81. doi:10.1016/j.ahj.2005.04.003. PMID 16442888.