You really can't lose with anything from Whelen. I've tried many different brands over the years, and Whelen stuff seems to be the most reliable. There are other brands that can be brighter or cheaper, but they don't last. We use Whelen Justices on a bunch of our trucks, and they are very good bars for the price. We also have some Liberty IIs, which are more expensive, but a lot brighter.
Stationary pylon all the way. The biggest advantage is that the lightbar stays pointing where it is supposed to. The second you tilt your bed with a bed-mounted pylon, the lightbar becomes worthless. Doesn't matter if it is blocked or not, since all the light is directed toward the ground and the sky. You do gain a little bed space, but the lighting aspect is the most important.