Yep - its a Big D - its a great pedal, very versatile - from a OD to a screaming distortion with a fuzzy diode too. I have a HBE Powerscreamer and prefer the Big D.
The Weeping Demon is the only Wah i've tried so I can't really say - it has all the bells and whistle's and does the business tone wise but its has a physically quite narrow area for the wah sweep - You can't really pump the pedal, you have to learn the spot and play there.