I've used both by themselves as well as in the rotation that I currently feed with, and their are a few differences that I've found (growth and color are not among them, fyi). First, the vitamin content of BGplus is much higher. If you feed almost strictly pellets and only one kind of a pellet at a time, the extra vitamins might be desirable. However, if you rotate through foods and feed a variety of pellets, shrimp, krill, veggies, fruits, etc. then in my opinion, the extra vitamins that they toss into BGplus aren't really needed. They don't hurt, but I'm not sure that they help.
The second thing that BG+ has (the reason for the "plus" ) is endospores from
Bacillus bacteria. Endospores are little bacterial "seeds" that contain all the genetic material of the bacteria, but are drying- and heat-resistant, so they can survive in the dry pellets for much longer than live bacteria could. Hikari claims that the bacteria germinate in the fish's gut and aid in the digestive process (much like probiotics that humans take such as Acidophilus, Keifer, yogurt, etc.) and decrease the total overall waste. I believe Hikari's claim that they aid in digestion because there is a HUGE difference in my O's poo when he's fed on BGplus as opposed to G. When on G, he'll poo out solid red masses of poo, something that makes me think he would be more at risk for constipation if fed mainly G. When fed primarily on BG+, his poo will be crumbly, for lack of a better word. There is less of it when I vac the tank, so much of it must be getting sucked up by the filters.
If you have sand in your tank, you might find the solid nuggets of poo that G causes to be a desired effect (easier to remove since it's all one piece), but the decreased chance of constipation is enough reason for me to include BGplus rather than G in my O's pellet rotation, and it makes up the largest percentage of the rotation these days.
If you feed enough wet food (veggies, fruits, shrimp, etc.) you shouldn't have to worry about constipation in a normal fish--unless you feed a lot of feeders, but I won't get up on that soapbox at the moment.
