I'd honestly take that over this, since at least that's a new alignment that would speed up new trips rather than just "add more lanes" to existing corridor (not to say this is a good idea, but I think it would be preferable).
That being said, how many roadway projects are there that would both be cheaper than this tunnel, and could easily be popular to many people? I know
@Northern Light mentioned that the MTO has a laundry list of highway projects, surely those would be quite popular, and would also have the benefit of being more targeted towards parts of the province he could possibly win votes in.
For me personally, something I would love to see happen is a reversal of many of the downloads that occurred under Harris in the 90s. Local politicians who were saddled with the cost of maintaining many of these roadways have basically been begging for the province to take them back since the 90s - and having driven on some of them, they are often in ROUGH shape. That and it could also help fix many OCD destroying discontinuities that confuse those that are unfamiliar with the highways such as Highway 9 in Orangeville, Highway 7 in York/Peel, and many others. You don't even need to reupload all of them, just some of the core ones that are important to intertown/city travel such as Highway 14 would provide so much bang for the buck.