It's a close call between those two and will most like come down to personal preference! I have never owned the Maxpect lights but I have had very good results with the Prime.
Looking at cold, hard specs alone, the
Maxspect is slightly more powerful with 65 w (vs. 59 in the
Prime) but has a slightly worse spread.
Nah, it's a close call in my book and I would not be able to tell you which one to buy! If that was the only two choices though,
I would end up going with the Prime. If those are the contenders- and if this is the price range, I would give the Kessil A160WE a good look as well.
That being said, I don't reckon any of those two lights will be powerful enough for
good SPS growth.. Have a good browse around for a used Radion G5 or a Hydra maybe? Or a used Kessil A360!