I've always gone with Alpine and I won't go with anything else. I've had their W202, W205, and I just bought a W900bt. I am currently selling my 205 if you're interested.
I think their gui is awesome, super fast iPod connectivity, edgy design, and its got nav and bluetooth. You can watch dvds on the fly and videos from your ipod and with a backup camera it'll show you what's behind you when you put it in reverse. It's audio features are top-notch.
I've had a little experience with pioneer units but to be honest i wasn't impressed with their navigation. However that was years ago so it could've improved considerably.