I'm favouring Juventus for advancing to the semi finals. I'm aware of how successful Sporting are in this tournament.
However Arsenal and Juventus are not the same type of teams. Each of them has a special kind of game plan for themselves. Sporting's game somehow worked well in the rematch and it led them to even eliminate Arsenal which were the biggest favourite team for the Europa League title. But Juventus' style can be really boring and maybe problematic at the same time. If Juventus outweigh them they can get past them narrowly on aggregate.
Juventus have a bigger chance to be in the semifinals. They have no more chances in Serie A so for sure they will put the Europa League as their focus to get the title. Juventus is also one of the teams with a big chance of becoming a champion apart from Mamnchester United, of course. In my mind it is very likely that if not Manchester United will be able to win it, then Juventus will be able to win it.