Pretty much impossible to say, since we have no implications on how strong Broly was at this point or how gradually his strength increased. Given how via scaling, his Base form as an adult should run circles around Freeza, I wouldn't be surprised if Kid Broly could beat the Tyrant as a SSJ.
I imagine Broli's power might be rivaling Freeza here. Unfortunately he is also an unstable nut case. I give this to Freeza if the two are even, based off him likely being smarter and more calculating.
But power wise, yeah, I think these two should be close together, based off nothing but my opinion.
Personally I think the only SSJ that cant beat Frieza is future trunks when he was sparring with base Gohan. He was the only one sorta established as a weak ol' rookie. The rest seem to have surpassed Frieza I think the same can work for Broly when he was a kid. If anything as his history continued he was being portrayed more and more as a prodigy.