Recording on a d5jw tape deck

Hello,
i have options and i would like to know best which direction i should be leaning i have a drum macine which puts out hardly any signal so im considering preamping it but should i be leaning toward line in where i have no input control or mic in which i do but then why a mix mic in whenever i run thru that i only see my vu meters on the left side and finnally i see l and r next to those phone jack or mic jack inputs how can they be the same yet different i appreciate your help