Pavel, what are your thoughts about how hard to pick? I watched your last "the bug" video and then watched that guy Roberto and you both picked much harder than I would (or did). I think I read in a book (possibly in that official Mark Knopfler Guitar Styles) that he plays light, not hard at all. I also played light and if I put some deliberate attempt at picking harder I quickly gravitated towards light picking again.
That's an amazing question actually. And a hard one, so please excuse me for the long answer. I think we need first to establish what "light picking" means. From my experience, often, extremely often I come across people who play too lightly, even including accomplished professional musicians! And I mean here more the "slow attack" or "fast attack", and not the raw force you apply to play a string. I think of it as the speed of fingers in the right hand.
The thing with guitar playing is, that the volume of your playing doesn't depend on the raw force you apply, it's more about how fast you attack the string with your fingers. If you'll watch classical guitar players, these guys usually have a perfect right-hand technique, but their fingers barely move, and the volume of playing goes all over the place: from quiet whispering notes to atomic explosions. How on Earth do they do that? They do that by changing the speed of the attack.
"Light picking" is actually a required skill in order to be a good musician because if you pick too hard, the excessive stress on the right hand will quickly drain your stamina and the hand might actually even get hurt in the long run. So picking should always be as light as possible and relaxed as possible, but the actual speed of attack may change.
From what I can see and hear, Mark has a pretty fast attack, he doesn't approach strings lightly at all. If you play his stuff lightly, it just doesn't sound like it's supposed to sound. Take "Marbletown" for instance. Mark hits those strings pretty hard in that song, he's not lightly picking it at all. So no, I'd say he plays really hard. But Mark is a big guy and I think this comes pretty naturally to him, so coming from someone like me it may feel like I'm forcing this attack. If you have big hands, chances are you will automatically pick harder.
So anyway, my view is that two things should co-exist somehow in guitar playing: the 100% relaxed right hand, but at the same time, the fast attack with fingers. But if you will force this hard attack, you'll lose your hand, and if you decide to play lightly overall, you'll lose the tone. So it's a fine balancing act and a hard, but crucial thing to develop in your playing, at least in my view.