Smith is certainly a populist. My argument with Corbyn and Smith is economic. First off with their unsustainable borrowing plans. To create a viable economy long term you need to balance the books. Corbyn isn't going to get enough taxes through his plans. If you're going to be an economically viable leftist you need to propose a true tax and spend system that balances the books, ie be clear what and who you're going to tax.
His plan seems to revolve around quantitative easing, which essentially means printing more money and devaluing your currency. In turn that means any imports will be more expensive, maybe much more expensive. The more money he needs and he needs a shedload for his spending plans, the more the currency devalues, the more you pay for goods because most of what we buy. IE you and me are poorer as a result, it's money out of our pocket because our money is worth less and everything costs more.
Secondly plans for a high minimum wage will hurt a small business like mine because I won't be able to sustain it. And it'll hurt many small businesses. Then there's sales jobs that you need to have a low wage and high bonuses to encourage productivity. Even in Communist Russia people were paid according to their productivity.
Now if he tackles those issues ironed out I'd vote for him as I want a government investing in our schools, hospitals and services.