As said before it depends on what / where you ride.
In terms of whether they are needed....
Some of my bikes have worked with droppers, some haven't. My Salsa Spearfish didn't work, the post never got used, so went back to normal post. My Cube Stereo wouldn't ride it without, it's up and down like a whores drawers!
Had this same discussion with the missus recently, when she swapped to a Cube Stereo 29, it came with a normal post, I offered to put a reverb on. She wasn't sure but I convinced her to give one a try and if she didn't like it then we'd take it off.
First couple of weeks, we hit Whinlatter, Gisburn and Llandegla, where she struggled to use the post effectively. Looking back think part of it was the new bike too. This weekend at Llandegla it clicked for her, she was using it loads, riding faster, hitting things harder, at the end of the ride she admitted, it had a made a huge positive difference and wanted to keep it.
From my experience I think you have to give them a chance and try them. You'll either click with or you won't but if you do, it will massively increase your enjoyment.
In terms of which post.....I've had a mixture of Reverbs and Command Posts over the past few years. The command post was simpler mechanically and needed less maintainence, but the reverb for me whilst a little more maintainence prone, is the slicker product and works better.