Zeplin is good in conjunction with Sketch (which is rapidly displacing Illustrator). Though Balsamiq has myBalsamiq, which is a browser-based implementation -- and if you haven't fully tested your user experience, it's better to work with low-fidelity wireframes (easier to throw away bad ideas, when you realize actual users don't think the same as your do).
But the question is not which tool to use for sketching UX ideas, but if there's a way to collaborate better, without tossing files (and avoiding the file_final.sketch and file_final_finalthistime.sketch problem). You can prototype in InVision, but you can't create mockups in it. Axure has a steep learning curve and high price, but okay collaboration; on the other end, a browser-based tool like Cacoo can do basic wireframes in the browser and allows remote team members to view and edit the same thing in real time, collaboratively.