I can't say I know for sure my percentages outdoors. I'm always grafting at peoples farms/forestry projects where my friend and I are turning their seedling trees into cultivars of pecans/hickory mainly and a few persimmons along the way.
At a lake that's open/subject to extreme winds, grafts of all kinds have blown out. When you're messing around with big scions and doing 3-flap or 4-flap or bark grafts... I would say the strongest grafts up high are going to be bark grafts before 3 and 4 flaps.
For sure electrical tape helps. Grafts wrapped with heavy duty budding strips will blow out more frequently. Mike makes a lot of valid points about this cutting instrument. It's quite excellent...
Furthermore, If I was going to start an orchard with 1/2" caliper stock or less of densely wooded species, I would use this tool, solely except where I could do a quick whip and tongue on more thin stock. I really like to use whip and tongue on pencil or less pecans. It's fast, efficient, and actually faster than using that tool to me.
A guy from South Africa wrote to me years ago and was in the process of beginning a Macadamia orchard. He had all his seedlings in place and asked if I recommended either the Fieldcraft Topgrafter or those scissor tools I like to call them from Scionon. I told him to get a Fieldcraft Topgrafter. He had I think somewhere near 1000 trees to graft. All must of went well. He had never grafted a single tree in his lifetime. Somehow he found me and I believe it was thru youtube.
It's a great tool. I can't say more good about it.