I think for the moment Balo but both in the long term, as Dzeko sounds like a really sound lad who with a good pre-season can come back a 15/20 goal a season striker for us. Once we work out how to play them both and utilise them effectively, there's no reason why they can't play together.
I even think Tevez/Dzeko would work but at the moment we're better as a 4-5-1/4-3-3 so I think Dzeko will just have to look at the long term, don't be throwing him into big games for the sake of it because he won't be match fit and he doesn't have a lot of confidence, build him up in pre-season against weaker opposition in a team that complements him and I think he will grow into being a great striker again, we know he is from his time with Wolfsburg and Bosnia.
Balotelli, well you never know with him but you'd hope he realises how working harder made such a difference on saturday and that he can try and keep that level up for the rest of the season and beyond, because he'll utilise his talent more by working harder and then he might develop into a world class striker, rather than one that many are unconvinced about, some hope will come great and some that have already written him off.
But for me the first issue is Tevez and whether he stays or goes should be done by June, get him out of the way if he wants to go or make sure we know he wants to stay long term and play ball, either way we can't do anything if we don't know whether he's staying or going during pre-season.