Basically....
35 "A" manual transmission 12 x 12 with clutch, no rubber mat on operator platform
35 "DA" hydrostatic transmission, rubber mat on operator platform, transmission range selector on FEL joystick, swivel seat.
My "D" has tilt wheel and telescoping steering column. I don't know if the "A" does or not.
Generally a "D" will run $1,200 to $1,600 more that a "A".