The first back squat image is almost impossible to attain UNLESS you are front squatting. Of course the pic is a back squat and a drawing so the laws of physics don't apply (you could rest the bar on the neck). This squatting style will build quads and some glutes (a traditional front squat will have quad and more glute plus be easier on the knees). It will place more stress on the knees and requires a ton of ankle mobility. Also be sure to drive the knees outward. That will clear space in the hips AND the ankles. Knees should travel WAY outside the foot. If you wanna squat like this then goblet squat and front squat.
There is a good reason for preferring our backsquat form to resemble FS as much as possible. The reason is that it's much easier to train the BS than the FS. Easier to do more volume. More reps, more sets. Easier to use more weight. This is because the FS depends on rack strength as much as it does leg strength and drive. If your build means you're leaning over, you need even more rack strength than leg strength. FS is not the solution.
Also knees out will force hips back and take you away from the olympic position. That's one reason why you don't want to do that in olympic squats.
http://www.youtube.com/watch?v=-V9MvP1nxOsGetting into the position will be easier. IME Olympic lifters don't really front squat in that position. That crazy position mostly comes from the catch phase in heavy cleans. Their back squats and front squats are more traditional.
You're probably familar with and looking at how US weightlifters squat. They're not very good at doing olympic style squats, for one reason or another, they end up adopting a very PC dominant style even with their 'olympic squats'.
Knees are not unsafe in a very forward style as illustrated in the first picture. The reason you might think that though, is because you haven't learnt to do the olympic squat properly
If you go from a PL style squat with vertical shins to an olympic squat, yes it will hurt your knees, even with the empty bar. The PL style doesn't depend on using the muscles directly around the knee and below of the lower leg. This is because you haven't taught your body the correct way to do an olympic squat which is very safe for the knees. PL style squat dont teach you to recruit the muscles of the lower leg to stabilise the knee at the bottom of a deep olympic squat. If you use your calves and hamstrings and quads (near the knee) and contract them while going into the hole, the knee is supported very well by these muscles. You just have to try this out yourself. Think of the muscles around your knee activating to absorb your descent into the hole and you'll find the stress on knees is reduced. The video above goes into this a bit too.
You'll notice one thing about these squats, there is a very tiny angle btw hips crease and the knees, the knees are almost horizontal as are quads. This means the quads are in a better position to act out of the bottom of a hole. If someone does a 'deep squat' like KingFisher or my front squats, this means the quads are not able to act immediately out of the hole since they are over stretched. That's bad. Instead in that case it's the glutes and hamstrings which bounce you out, and then the about halfway up quads kick in. This isn't a quad dominant olympic squat. That's why I was going on about depth being misunderstood, because for the purposes of an olympic squat, it's more about the depth of the knee rather than the ass vs the knee.
The second image is more balanced. You will get quad and glute work (although lesser) and hamstring strength. All 3 are needed for athletes who run so this is the more common approach. It also allows more weight so ou see it is more similar to a power lifter squat. Starting strength is a classic example of this style.
Depends on the person! My HBBS are so hamstring dominant, hell even my FS are so hamstring and glute dominant that my attempts at olympic squats end up resembling the 2nd pic. It's a fault. Because in my case the weight is not directly over midfoot, it's ahead, sometimes even further than my toes. This leads to good morning squats. Not enough training for my legs. Not enough quad development.