Federer I think would be a shoo-in to get wins over both in the same season assuming they played 10 seasons together, assuming they play often enough. Djokovic could get wins over either (50-50 or slightly worse on clay, maybe 30-70 or 20-80 on carpet), so it would depend on how often they would meet for it.
If we assume there is a maximum of 3 clay meetings and a maximum of 2 carpet meetings each year? Then I think that Federer would get a win over Bruguera in at least 7/10 seasons, Djokovic 8/10 seasons, and Nadal 10/10 seasons. Against Sampras it's 7/10, 4/10, 2/10 respectively.
So I think all 3 could do it, but for Nadal it would be fluking a couple wins against Sampras on carpet in his best years, while just dominating Bruguera. Eventually he'd break through. For Federer he'd be more or less 50-50 against both Sergi and Sampras (maybe a little worse off, but not by much), so eventually it'd line up. For Djokovic he'd be pretty much 50-50 against Bruguera too, but much worse against Sampras. Sampras would definitely be better, but I don't think Djokovic wins would be uncommon, just maybe like 2/3 times Sampras wins.
Probably Federer >> Djokovic > Nadal in terms of chances though.