if you read issues 338 and 339 they both knocked each other unconscious but the heat of the planet revived bill for few seconds i which he rescued thor was transported back to asgard and immediately collapsed again.It was made clear even from bill's own mouth the only reason he revived was due to heat from planet where they fought(being similar to the environmnt of his home planet,indeed he says in no other place could i ever have won so close a contest(it's the equivalent of them fighting in a freezing icy environment and thor reviving due to conditions suiting him.I don't think bill gained any strength from his transormation into beta ray thor just thor's other powers.They also fought few times during thor's warrior madness run and i think thor took him out once.I think it could go either way but i do not think bill can call on the godblast like thor(might be wrong about that)however towards end of oemings run thor had learned to produce some of his powers even without hammer which might give him the edge.