My personal favorites are these. They are what I have on all of my bridles and they're the only kind I'll buy anymore. Mostly because they are the same basic quality as Herman Oak leather...but without the price
. I always go with 3/4 inch width because that's wide enough to have good weight and feel but not heavy enough to feel bulky in my hands. NRS - 3/4" x 8' Water Loop Ends Split Reins - NRSworld.com
Another thing that wasn't in my first post that I've seen other mention is the safety factor in a fall. As stated, there is no chance of a horse getting their foot hung in the loop of the reins. At worst, they might step on a rein and break the water tie, which is an easy fix. With 8 feet hanging there, it's easier to keep hold of a rein to keep them from running off.
I suspect the reason that so many people are taught "drop the reins when you fall" is because of the fear of pulling the horse down on top of you. I've seen that more times than I care to remember with roping reins but I've never seen it with split reins. I'm sure it's still a possibility, but with splits, then the reins are just more likely to slide through your hand a little as opposed to putting all
your weight on the horse's mouth when your hand comes to the middle of them.
Very similar to what is seen in this video at :58 and 8:15, except the horse falls right on over.
And, like others have mentioned, there is 8 feet of play there for how long you want your reins. You can have them up snug for contact or you can have them draped nearly to the ground. You can loosen them for a horse to drink out of a creek or a tank without having to bend over and stretch your arm down their neck to keep from losing them.