Solar City (SCTY) may have Tesla's (TSLA) - Get Report Elon Musk in its corner, but First Solar (FSLR) - Get Report will likely shine far brighter, advises Jim Cramer, portfolio manager of the Action Alerts PLUS Charitable Trust.

"Solar City is controversial and I know there's always going to be backers of it because it's an Elon Musk company," Cramer told TheStreet's Rhonda Schaffler at the New York Stock Exchange Friday.

Larger rival First Solar is the better pick in the alternative energy space, though. 

"I'm a backer for First Solar because they have the best business model and have very good earnings," Cramer explained. 

First Solar will report its first-quarter earnings after the bell on Thursday, April 28, while SolarCity is scheduled for its release on May 3. 

Solar companies have taken a beating recently, dragged on by SunEdison (SUNE) which has been under scrutiny for financial discrepancies. Missouri-based SunEdison announced earlier this week that an investigation into its accounting had found no evidence of fraud, though shares remain nearly 100% lower since the beginning of the year. 

FirstSolar is down 10% since the beginning of the year and has fallen 7% over the past 12 months. SolarCity has fared much worse: shares have tanked 43% year to date and are down 48% since this time last year. 

For comparison, the S&P 500 has added 1.7% since the beginning of January, but is down 1.4% since April last year.