it's absolutely true that methanol is more acidic than water.in chemistry or any other science we execute experiments and then come to conclusions and then propose an explanation,it's not the reverse.the apparent justification given to this phenomena is that since the charge density on the methoxide ion is higher than hydroxyl, so it's slightly more solvated and hence stabilized,hence making methanol more,just slightly more acidic than water.the steric hindrance of both the molecules is nearly the same and hence that factor does not count.Even i didn't digest this at the beginning but we cannot expect everything to go by theory.We have to face few exceptions like this.