Well, currently it is 1 hour vs. 4 hours.
But seriously, I guess it depends on your game style. For example, when do you find PCs wanting to take a short rest? IME, it is often during a dungeon crawl etc. when you are likely to run low on resources and need your "breather" to spend HD and regroup. In such situations, I am still using random encounters/wandering monsters, which can interrupt the short rest and make you start over.
Case in point: in our prior session the party ended by returning to their camp and needing some rest. So, we picked up at that point on Saturday when we played and 2 hours into the rest a random encounter found their camp and a fight ensued. Those two hours were wasted and they had to begin again. By the time the next 4 hours was done and the rest complete, it was too late for them to return to the dungeon as night was approaching. So, they decided to travel back to the keep and had another random encounter along the way. Barely rested, they battle went south for one of the PCs, and by the time they made it back to the keep they
really needed a long rest. So, 36 hours later (the required 24 plus waiting until the next morning) they left the keep to return to the dungeon...
If I was still using 1 hour short rests, that first random encounter wouldn't have interrupted the rest because it came on hour "2" of the 4.
Since we've made this change, you really do feel the difference IMO between 1 hour and 4 in most cases. Although we are considering dropping it to 3, we haven't decided on that yet.