RE:RE:RE:RE:ALA vs. BLXBoralex is a company that's capital intensive with a relatively high debt and inflated multiples (PE, Cashflow, EBITDA, etc). The only reason it could be considered cheap is because it is in a sector that's more attractive at the moment. The share price will vary more due to the market valuation of the sector than due to earnings/EBITDA/cashflow/dividend growth, which makes it unpredictable. Imo, in that sector, there are better opportunities elsewhere.
I don't even know why someone would compare Boralex with Altagas, since they are very different. Altagas trades at attractive multiples, will likely grow their PE, cashflow, Ebitda and dividend per share faster than Boralex for the next 2-3 years.
In an investment portfolio, Altagas is the rock that can be relied upon in all market conditions, generating value growth year after year. Boralex is the company in a hotter sector that will see wider swings in its share price based on the market exuberance for renewable energy. Both have different risks and drivers and should suit a different need in your portfolio or investment style.