By "major in neuroscience" I assume you mean "major in biology with a concentration in neuroscience" in which case your curriculum will be
this. In that case, consider that if you take BIOL 121 you will need to take BIOL 230 as well, whereas if you take BIOL 101 you will need to take BIOL 102. While 121 is more demanding than 101, it seems like (from PCR) 102 is more challenging than 230. Also, 121 is generally recommended or encouraged for those who intend to major in biology or pursue it more seriously. Just something to think about it.