I don't think either party will be more or less successful in that regard, all depends on the world oil price. No matter which party is elected, TMX should be under construction again this summer, and Line 3 will be in service in the spring, barring unforeseen circumstances.
The style of investment that drove the boom - massive oil sands capital spends on new facilities - is largely over. This was foreseen all the way back in 2011-12 ish by CERI, when they forecast maintenance spending would overtake newcapital spending on the oil sands in the 2017-2019 period, which has only been accelerated by the Texas light boom of the last 4 years. Drilling will pick up as the storage glut is cleared by extra pipeline capacity and curtailment fades, but I doubt it will put a spring in the producers step over lets 2018-19 drilling levels.
I don't think we will ever see recovery of the lost jobs in oil and gas, as companies have learned to get along with less by outsourcing and automating. The attracting new investment and industry side, I see the corporate tax cut proposed and the tax credits proposed as different sides of the same coin, neither is better or worse.
It may seem fatalistic, but the provincial government can only do so much to dig the province out of a situation the provincial government didn't create. Alberta took on the oil price shock, and it was compounded by the transportation problem, but we can't fix the first, and the second is well on its way to being fixed already.