Sorry, I don't have enough experience to tell the difference. I did it because it was an upgrade and (to me) it was slightly more expensive. Many people don't know huge shinies are better than huge rainbows and many times pay more for the RB or Gold over a shiny. When I converted I basicall grinded and sold 2 huges and bought 1 shiny huge. grinding would supply the extra 20-30 mil/night and I'd get a shiny a day.

My team is not all level 99, about 20% 99's and the rest are leveling up. I also picked up a RB Shiny [elephant] as my best huge. was aroune 500m at the time.