With how thin those pads are, you might as well just wear a sweatshirt. You bail and your knees will be done. Believe me, knee pads NEED to be bulky if you want your knees to last. Either way, knee pads will never last you a lifetime. I buy a set of pads and wear them til they are in pieces. Usually takes me a good year before I have to buy a new set. Just think of it this way, would you rather spend $25 a year for bulky pads and good knees later in life? Or live life when older with knees that are shot to hell because you wanted to go for a slimmer pad that won't do shit if you bail onto it? I'd take the $25 bulk pad option any day.
I'd recommend ProTec pads. They are the most comfortable, lasted the longest for me, and do their job very well. This is from experience of my last two sets I've bought. DO NOT buy Lizard Skins, they are terrible. The stitching on them sucks, and the plastic pads rip off kind of quickly. What took my Pro Tecs a year and a half for the plastic to start ripping from fabric, took my Lizard Skins about eight months. Plus Lizard Skins tend to slide down your legs after using them for a few months.
EDIT: To Matt's question, pads feel like they "get in the way" at first, but you get used to them after awhile. It does up my confidence when trying something big. Because I know if I need to bail I can just jump out to my knee's. Similair to a BMX or skateboarder on a vert ramp. You never see them run a trick out. They always go to their knee's. It's easier, and your body doesn't take so much of the impact. Depending on how high of a drop it is, of course. As for my recommendation, it's right above this EDIT line.