Well it seemed to me that in the flash back Trunks was struggling a bit against Dabura but then he went SSJ2 and essential one-shot him, I reckon Vegeta could wreck Dabura that easily as an mssj. But the question is did Trunks get a lot stronger after that battle, if the answer is yes then I'll lean towards Trunks, if the answer is no then I'll go with Vegeta.