Ah thanks. I think that Forerunner 305 gives total ascent as well in the PC interface form, but I never download my rides to the PC.
The Training Center software will add the elevations up and arrive at it's own total ascent regardless of whether or not the unit kept its own total. The main difference is that the 705 and 305 have the barrometric altimeter and accept accessories while the 605 and 205 do not.