I have used both at different times for different reasons. a slip collar, is a must for escape proofing in public. and the rolled 1 inch Timberwolf brand can be worn loosely at all times.(be very careful with pups as they may not know to not jump off heights with one on and can chock,make sure they are sensible about those things before using one unattended) I hear a lot of folks say--he/she never ran off before!!
but one day they WILL in a panic situation !! and for harnesses, the rule of thumb is --they teach a dog to PULL !! only after learning how to walk politly on a leash should a dog be put into harness some of the time. and yes,,IF that harness isn't tight enough to only put 1 finger under and between it and the dog, is it tight enough!!!THE PROBLEM ANY DOG LOVER SEES is dogs wearing these 24/7 or when it is hot outside,--(we shouldn't have this breed out in that heat anyway)
the only halter that has worked --VERY WELL --for pulling dogs is the Easy Walk dog harness-(here is the link,and sizing is on the page,-the ring to connect the leash to is on the front of the chest, so when the dog pulls, it pulls the dog back towards you-<)https://www.premier.com/store/Products.aspx?cid=1&pid=6> and I believe is said $24.00. these work so well quickly. you will have to use your common sense to pick the collar time and type to use, this is what I have found to be the safest, and yes if you are walking by all means use a halter.But make sure it is adjusted right. have fun and be safe.