anthonyUK said:
Theoretically it should be better as it is easier for the yeast to metabolise Dextrose but I think in practice there is little difference.
Not so. In practice it's very different.
To cleave the bond of the two saccharides in sucrose, yeast will secrete an enzyme into your must or wort (it doesn't actually do this to cleave ALL the sucrose, some gets done intracellularly, some extracellularly. Dextrose being mono-saccharide has no such bond to cleave and so there is no secretion of said enzyme.
The really puzzling bit however is that maltose (the disaccharide in wort) is taken into the cell and cleaved rather than the enzyme being secreted outside of the yeast cell...
Whether it is this that has a bearing on the by-product flavours or not is, as far as I know, unproven but it certainly seems plausible on the grounds that there are two clearly distinct metabolic pathways for sucrose Vs other sugars.