Expert opinions? Which has been proven to be the healthiest: a low-carb, hi protein diet or a lacto-ovo vegetarian diet?

Ideas vary. Different folks here will make different recommendations. Things seem to be shaking out recently in favor of the mediterranean diet, which is none-of-the-above. Especially, don't think that diet is so magic that it will make it unnecessary to exercise, otherwise live a healthy lifestyle, or ignore your personal physician's advice about your special health needs. Glad you're proactive.