I think the slope matters, as discussed a bit on the Muirfield thread about hole no. 16 and adding slope, I think to the back left pin there.
I asked all the pros I know about it, and yeah, back is always harder. If they have an open front angle, and are between clubs, they just use the lesser club for an uphill putt. If coming over a bunker, (which they seem to prefer over risking a driver to a fw edge that misses) then they take the longer club and use more spin. They will use a back slope to direct a ball to the pin, but Lanny Wadkins once noted that the very back of the green edge could be too steep and cause a ball to suck back too far. Again, I was never able to figure out exactly what that slope would be, but gathered it would be the last 10 feet sloping up over 3% or so.
JN once opined that about the only time he would hit a running shot (or low spin, relatively speaking) was on a long par 4, downwind, 2 tier green narrower at the back, and he would try to "chase it up the slope to the pin." I gathered he wanted it to hit the widest part of the green to avoid hazards, and use contours to get it there, much like Lanny would use contours to move a ball sideways on the green towards the pin.
I still wonder about a downhill, downwind shot with the pin at the front behind a bunker. The two natural factors tell you to club down, but the bunker tells you to club up, if there is ample room behind the pin to play safe. It just feels counterintuitive to have long be safe.