r/stbernards

So my spouse and I want to buy a huge dog and we were thinking either st bernard or the english mastiff. We have two cats and are planning on getting a puppy because I've heard both breeds need to be trained early. Has anyone had both before? How where they different? Is one harder to train? Is one better with cats than the other? I've been trying to look this all up but it would be nice to hear from someone whos raised at least one of these goofs.