It's also, to a certain extent, about how long you are going to wait at triage in the ED. I had a chest pain about 1/4 mile from the ED yesterday, and ended up grabbing an ALS crew clearing from a call at the same facility--which I wouldn't have done 2 years ago-- simply because we waited nearly 30 minutes for a bed, and it was good to have a 12-lead before arriving at the ED, which was well worth sitting on scene for a few minutes. We tried several times for an IV as well, but nobody could get one, so we held off on the nitro and stuck with Aspirin.
It was unexpected, but the EDs were absolutely packed today, and partially as a result of the DPH ban on diversion, we knew we would be waiting.
Long story short: based on a lot of factors, to include distance from ED, patient complaint, patient condition, crew comfort, ED wait time, etc.