Im not sure if I am reading you query correctly,
"Grounding at the plug" implies that the Ground (-) Line inside the wall socket is being used for surge protection for the placed ird.
While this provides static protection, it also,
a)Requires a licensed Electrician
b)Compromises House-to-Ground balances for designated circuits
c)Puts your Nieve Ass out to line, because according to NEC ground rules, (for lack of better words) that ariel device, inlcuding all properties of the device, line and all other operating doowickies, must include a ground less than 50% of the shortest system run of system, of proper ground guage, attached to something other than my house, next door, and whytheFU am I answering such a dumb damn question.
I really dont give a sh*t of you do your job right or not - i mean, your lack of smarts just creates more jobs, Right?, I guess that there is nothing on TV while travelling doing what I do, so like many "re'sponder-ers" Im just killing time.
So,
Dont ground at the plug, man, go shock yourself and think out loud "damn that hurt", and rule out the possibilities Homer. DOH!