it's not a done deal yet but Inter has the advantage over Juve, who don't seem to be pushing for the player anymore, maybe because they don't think he is worth entering a bidding war with inter and falling into Pozzo's trap.
At this point, Barca and City probably have a better chance of signing Sanchez than Juve with Inter being probably the overall favourite ... from what I've read, Inter are offering close to 20 mil+Mariga+Santon and even Gaston Ramirez could be included (from Bologna to Udinese via Inter) ... whether full rights or co-ownership for Ramirez it's not clear yet. Juve on the other hand has come up with a similar offer in cash but the players they are offering are not as well liked by Guidolin as those offered by Inter.
Add to that Sanchez' personal preference for Inter - CL football, I guess - and Juve would have to cough up more money than he is probably worth, both in transfer fee and salary, in order to beat Inter to his signature.