I can see how one would think the Widow and Habu are a lot of like at first glance. I thought the same thing about Schafer and Tall Tines.
However, I have Widows and Habu. There is a world of difference. The only similarity is the face-mounted limbs.
Habu limbs are more narrow, limb tips are different (blunted), face to back of the riser is less wide on the Habu. The grip on the Habu narrows to a point at the heel more than a Widow.
My Habus (I have one TD and sold another TD) have far more stable limbs which really shows itself when stringing. I think Widows are great bows but they always scare me when stringing them (yep with a stringer) for fear of limb twist.