AI vs live cover - I would pick live cover. I have had 2 experiences with AI - one bad experience and one not so great. During our first breeding, bacteria was introduced into the uterus and my mare came down with a terrible infection. The pregnancy took, but somewhere along the way she developed a placental infection and we lost the foal. The second time, AI was used, they induced a heat cycle to try to get ovulation and the mare came down with colic. We do have a foal who is great. However, "easier on the mare" that is totally subjective and was NOT my experience. I think nature probably has this department perfected and live cover wins hands down.
P.S. With AI the risk of multiples goes up, risk of infection goes up, and I do not think the % of viable pregnancies actually increases with AI. Check that fact.