Ummm, the arguments are generally whether or not there are two sexes or a shading of say, black and white through gray and maybe even some colors between them.
Gender spectrum is a bit more complex. Plus there are arguments about whether or not gender is a totally socially-constructed matter or whether there are essential elements of gender built into our heredity and biology. To what degree are those elements combined, etc.
Many TSes and many TGs (includes TSes along with other people identified as TV, CD, DQ, Androgyne, Neutrois, etc) find their beliefs to be spectrum. Others are inclined to binary, one of two.
The arguments often become attached to political or individual identity concerns as well. To tell the truth, some of the best writing, that remains pretty even-handed throughout and always reasonable, I have found in Julia Serano's essays collected in her recent book, Whipping Girl: A Transsexual Woman on Sexism and the Scapegoating of Femininity. It's available through Amazon at less than $11 and would be well-worth your expense.
N~