Sorry, I commonly refer to the long axis as the Y (my table was 10 feet long) and the short was the X (6 feet) - unless I've got those swapped...it's been 4 years.
What I found on the y-axis was where most of the slop was. I never did figure out if it had something to do with it being responsible for the weight of the entire x gantry or if it was somehow related to the sheer repetitions. Anyway, in my case I found that the rack and pinion gears wore faster, had more slop more often, and was the source of most of my problems.