But advantages of a horse would be not taking as long to clear or plough or transport anything as for oxen -and I think horses generally have a longer serviceable life span -20 or so years - don't they?
Agreed horses would be faster then oxen. But then we don't usually time field plowing.
I also agree horses would have a longer life span. But then if whatever we use is being bred for replacements, then lifespan may not be as important.
Part of the reason I think oxen may be a better choice, is our own poineers, in many cases, used oxen rather then horses for farm work. I assume since they had the choice of either, the oxen were considered the better choice. I always thought it was in part because they could eat what they do not use to work the field, and as I pointed out earlier the norm was to drink cows milk rather then horse milk. So with one animal, they have their tractor, a replacement animal they could and were used to eating, milk they were used to drinking, and an animal without some of the extra work a horse would require. Don't have to put shoes on a cow or trim it's feet.
PS hunter -they have horse milk dairies in Belgium but of course with horses they keep the foals, because unlike cows, mares stop producing milk if they lose their foal.
This is why I thought the cow better. You get more milk, and if you need the cow for farm work, you can do that and still feed the calf from twice a day milkings. That's the down side of a horse. A bottle fed foal is a pain, something they wouldn't want to hassle with, and being bottle fed it's always slower getting bigger.
Given a choice I'd take a horse, but for Iowanic's story, it seemed to me the cow had more benifits and a smaller downside.