I have a pair of Justin boots, similar to Ariat's Fat Babies. (or whatever they're called.) They work well for me - I'm fat and my calves are too big for anything with a higher shank on it.
One thing to be aware of though - if you wear your boots to work - do NOT sit at your desk with your heater going under your desk, the day after you cleaned out the barn and hen house. Trust me, your co-workers will NOT appreciate it!