Turkeys, unlike deer, are very alert to airborne predators, I think your chances are better when concealed on the ground... however, depending on the foliage, it may be easier for YOU to see the birds and get a clear shot. I would not call from a treestand, unless it is before fly-down to get them moving your way and then go silent after fly-down. I would not use treestands for turkeys as it is too limiting and makes fast repositioning impossible. All of my favourite hunts have been playing "cat & mouse" with toms in the timber.