Virtually all the modelers in my area (including me) are gravitating towards 58's. If you use bamboo skewers to uncouple, the 58's are better than the 5's.
If your track is rough enough and your coupler height varies enough that #58's uncouple just moving in a train, then you have way more problems than picking which coupler to buy.
58's look better than 5's. Throw in semiscale wheels and it really improves the looks of the car.