Hi there,
I think both are excellent long-term holds and given the shift towards renewables, it is a space that will see considerable growth.
We have BEP on our foundation list as we just think it is best in class. Brookfield is one of Canada's premier capital allocators, and BEP is top notch. NPI has been one of the fastest growing renewable companies, and is also a high quality stock to own.
In terms of growth, NPI has higher expected growth rates with average revenue growth of around 28% over the next couple of years, where as BEP's expected growth rate is sitting in the mid-teens. Of note, NPI has a much stronger history of meeting/beating estimates. It has beat in 9 of the past 12 quarters (including 6 straight) whereas BEP has missed in 10 of the past 12 - something to consider.
When it comes to valuation however, BEP does seem better valued. It is trading at 2 times book value, whereas NPI is closer to 7 times. BEP is also cheaper on a number of other metrics. Combine that with a slightly higher yield and today, I'd lean towards BEP. However, both make excellent selections. Once could argue for owning both - BEP for value and NPI for growth. It depends on where they fit within your investment goals.
Mat