Front or back clip harness?

My pup’s collar he got from the breeder has been unclipping randomly while we’re outside so I went on woof and ween and purchased him a harness. It is still coming in the mail, but today we had orientation for puppy school and the trainer said he doesn’t recommend back clip harnesses only front clip. I read that the front clip harnesses can cause chest and shoulder issues so I am unsure now what would be best for him. All the dachshund websites I look at seem to only offer back clip harnesses, is there one that works better for dachshunds than the other? Trying the best I can to help his little back.