Our dog comes with us on trail rides and isn't leashed. He's sort of a velcro dog. Black and tan, heeler and corgi. 95% of the time he stays right behind the last horse. He doesn't chase deer, rabbits, squirrels unless he actually stumbles upon them. Most of the time they are long gone before he gets there. He comes like a champ. 100% reliable.
Right now, we have a lab who is 100% most of the time... until he sees a bird, car, person, other dog... you name it.(Not to mention the possibility of a female in heat, where I think ANY recall would breakdown). Our corgi mix is worse - she picks up a scent and will disappear for hours. Our third dog (mutt) is probably 90%, but is also very protective so I wouldn't trust her loose with strangers approaching. The lab or mutt I would take trail riding only if I was on a secluded trail without the chance of running into people or being near a roadway.
Some years back I visited Vancouver, BC. This is a very dog-friendly city. I was amazed at how many people were walking through the busy city with unleashed dogs. The dogs were not distracted by any of the hustle and bustle - they just followed at their owners side as if they were the only two lifeforms around. Again, I envy people who can train their dogs like this.