Bear in mind, I'm just transitioning from operating an excavator (as I've always been an excavator operator) to using a skid steer. One thing that struck me as odd is this: some skid steer lift arms are designed like an accordian to allow the bucket to reach very high. In cases where it has to load a dump truck. But others' lift arms are designed to look like any trpical front end loader. To illustrate, let's take for example... this: The CASE Minotaur DL550. See how when it raises it's bucket, the design of the lift arms function similarly to an accordian or a mobile scissor lift machine? Then there's... The CASE TR 340B. See how it's lift arms resemble a typical front end loader? What's the rhyme or reason behind these different skid steer lift arm designs? And I apologize if they are track loaders, but it was the best I could do on such short notice. And they mostly bear the main base body of a skid steer loader, so I assume it's ok to post this machine under Skid Steers.
I believe it's more about break-out forces.
Search the forums for "radial lift", and "vertical lift". In a nutshell, radial lift buckets travel along an arc while raising and lowering, and vertical lift buckets move more in a straight up and down path.
Historically, the radial lift machines (your second pic) were designed for heavier pushing, excavating, and dirt work, whereas the vertical lift machines (first pic) were more for lift and carry type operations. The conventional radial design is just more rugged. Over the years the technology has gotten better on the vertical lift machines so they are a lot more robust now and hold up to digging/excavating better. The early vertical lift machines such as the Bobcat 7753 and early New Holland skid steers would really fall apart if you pushed them too hard digging.
I heard it explained this way. If most of your work is eye level and below, get a radial lift machine. (more rugged) If your work is above eye level, then you want a vertical lift. (more lift)