Much depends on how severe the lateral bends are and where they're located at. Walnut corrects very well with either type of heat. And hold corrections really well also.
For lateral bends, I like to get the bow to rough bow shape, limbs just barely bending, then correct.
If the corrections are, say, from handle to mid-limb, then I would use steam. A pryamid vs a rectangular design would make straightening easier. Pics sure would help...........Art