A 48 inch Photon V2 is 220w, a Pair of Hydra 52HD is 240w total.
Since you are not running them at 100%, the difference may not be that big. The price difference is very big.
The Photon v2 comes with hanging hardware and legs, the Hydra does not, which also affect the final cost.
I can assure you that photon v2 is more reliable than Hydra52HD.
I run a 24" V2 over my all glass 32 gallon. The thing is amazing. My only gripe with it is not being able to log on from my laptop and change the lighting schedule. You have to use the remote which takes a little time, but wouldn't defer me from buying this light again if/when I upgrade tanks
I had a Photon V1 a long time ago and it was a phenomenal light stuff grew great in my 45g, I upgraded that tank to a 65g and the 24" fixture I had didn't really work well( I couldn't hang it in my apartment at the time) so I upgraded to kessils
I've been running a 48" Reefbreeder Photon V2 for a little over a week now. I replaced a non dimmable Amazon 8x T5 fixture with it. Only up to 35% max right now. I was seeing less color in all my corals under the T5's, was running ATI bulbs, already seeing better color. Time will tell.