As a brand new cave diver, I've been talking to a number of people about the different strategies they use for indicating navigational information, whether that's on the main line or involving T's or jumps. One person suggested that there may actually be regional differences, perhaps related to the relative complexity and large number of entrances possible in the caves in Mexico. We thought it might be interesting to run a poll, to see if there appeared to be any consistency about how people do things, depending on where they were trained.
I think you need to specify under what conditions people use either kind of marker.
It's not sufficient to simply say one or the other.
GUE has the guiding principle when dropping a marker of any kind of "not changing the general navigation of the cave"
That generally means if the last arrow you saw was pointing into the cave, don't lay an arrow that is now pointing out of the cave (use a cookie instead, possibly with an arrow pointing into the cave)
If the arrows are now pointing "into" the cave (from your perspective), dont lay an arrow pointing out of the cave
mark T's or arrows pointing opposite your direction of exit with a cookie on the exit side of the line.
I dont know the GUE jump marking procedure.
Many people state to "never use a marker you did not lay" as a reference, which is a great rule, but under stress and limited vis/time pressures, it's very easy to get confused/make a mistake, and if 1/2 the world has just been laying arrows that were convenient to them (at the time), then it would seem that there is far more chance for accidents to happen.
All the caves I dove in mexico seemed to be marked pretty consistently (although there are some issues with certain divers thinking they can just move the mainline and/or markers around to suit themselves)