That's not a myth, it's a fact and reaction time has nothing to do with it. You're not consciously pulling back, your muscles will simply stop contracting for a short bit after which you (hopefully) disconnect.
The DC damage is a condition called 'muscular tetanus'. The main risk with AC at medium voltages (say 40 to 250 V) is that your heart goes haywire. Though those voltages could easily kill you too.
Yes, you should always be careful. But DC is most definitely more dangerous at the same voltage once you get over 48 V DC (the so called 'safe voltage', but that's a misnomer because under the wrong conditions voltages lower than that can still be fatal). The critical component by the way is current not voltage. Voltage really doesn't kill but current will. AC voltages are typically reported RMS, whereas with DC the 'peak' is also the average. Assuming the DC supply can produce as much current as the AC supply.
Being shocked by neither is good. But the choice between 200V DC and 200V AC is a fairly easy one for me and I've been shocked multiple times by both during my very long time of taking stuff apart and fixing things (yes, I try very hard to avoid that). The AC ones were mostly non-events, the DC ones were (even at lower currents) things to remember years later. Quite possibly that's not correlated with safety but it is definitely a data point (or rather several of them). Avoiding being shocked is a very good way of never having to find out how accurate this all is. One particularly memorable incident was hooking myself accidentally to the HV supply of an old tube radio. Don't do that. And be extremely careful with capacitors and DC batteries, they can supply a ton of current long enough to kill you. HV transformers much less so. (At least, the ones that you would normally encounter outside of industrial gear). And I suspect that the internal resistance of those supplies has a lot to do with whether you're going to be dead or writing about your experiences because it has a very direct impact you the current resulting. HV AC supplies that will supply very high current are hard to find, usually are transformers with relatively thin secondary windings. A battery pack like this is made to supply 100's of Amps at 100's of volts. That's lethal, make no mistake about that.
You kind of jump around from point to point. If your hand is wrapped around a a source of electricity (Assuming that it's not static charge and can provide a current equal to the source voltage over your bodies resistance) I'm sorry but you are not going to let go, even if you are hanging from the wire. Until a formation of soot has formed and the oils in your hands have burned off to increase the resistance, there is no letting go.
Let me give a couple of reasons why AC just as dangerous as DC.
1) Your body shares some of the same characteristics a capacitor, a capacitor with small capacitance, but one none the less. This means that an AC current can shock you without forming a classical circuit that would be needed for a shock from DC.
2) You mention RMS as a reason why AC is safer? The root mean squared voltage of AC is going to be less then the peak voltage induced by the name plate voltage. Wall socket voltage may by 120V RMS but will peak around 170V.
3) With a peak voltage of 170V the current through a resistor (like a human body) is going to be ~40% greater than that of an average 120V for DC. Stating that current kills but voltage doesn't is also ridiculous (unless you are talking about static charges). It would be like saying that the flow rate of water down a stream is dependent on the amount of water in the stream and not the speed of the flowing water. The fallacy is also point out in the link your provided.
4) Hearts are much more likely to suffer from complication due alternating current than from direct current
Again, I stand by my initial assertion, both AC and DC are just as dangerous. Anecdotal stories, while entertaining, don't mean much considering that you may have been hydrated while dealing with DC, which can increase the bodies internal resistance greatly. You may have been more grounded, you may have been touching a piece of metal that was grounded, the circuit may have been created across the chest which gives a nasty shock. There are many external variables which can alter your perception of what it feeling like while being electrocuted.
Reminds me of two major events in my youth. Like you being shocked by the HV rail of an old tube radio and another acting as the ground for an old floor polisher in my grandpas shed. I guess I preferred the 115v AC, I remember it kind of like a massage chair but all through my body. Luckily my brother knocked into me long enough to let go, not sure I could have otherwise. The radio was brutal, knocked me back across the room leaving my hand aching for a bit, scared the beep out of me.
i got electrocuted by 240v ac 50hz more times than i like to admit.
turns out its easy to disconnect, never held it more than 2s and its relatively painless.
never went near dc hv stuff with isolation so never got a chock from that yet. i intend to keep it that way
The DC damage is a condition called 'muscular tetanus'. The main risk with AC at medium voltages (say 40 to 250 V) is that your heart goes haywire. Though those voltages could easily kill you too.
Yes, you should always be careful. But DC is most definitely more dangerous at the same voltage once you get over 48 V DC (the so called 'safe voltage', but that's a misnomer because under the wrong conditions voltages lower than that can still be fatal). The critical component by the way is current not voltage. Voltage really doesn't kill but current will. AC voltages are typically reported RMS, whereas with DC the 'peak' is also the average. Assuming the DC supply can produce as much current as the AC supply.
Being shocked by neither is good. But the choice between 200V DC and 200V AC is a fairly easy one for me and I've been shocked multiple times by both during my very long time of taking stuff apart and fixing things (yes, I try very hard to avoid that). The AC ones were mostly non-events, the DC ones were (even at lower currents) things to remember years later. Quite possibly that's not correlated with safety but it is definitely a data point (or rather several of them). Avoiding being shocked is a very good way of never having to find out how accurate this all is. One particularly memorable incident was hooking myself accidentally to the HV supply of an old tube radio. Don't do that. And be extremely careful with capacitors and DC batteries, they can supply a ton of current long enough to kill you. HV transformers much less so. (At least, the ones that you would normally encounter outside of industrial gear). And I suspect that the internal resistance of those supplies has a lot to do with whether you're going to be dead or writing about your experiences because it has a very direct impact you the current resulting. HV AC supplies that will supply very high current are hard to find, usually are transformers with relatively thin secondary windings. A battery pack like this is made to supply 100's of Amps at 100's of volts. That's lethal, make no mistake about that.
That battery bank cost $7200, 2005 or so prices.
More than you ever wanted to know:
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html