The benefits of balanced AC depend on the component plugged into it. When I had the SFL2, both myself and a friend almost simultaneously said, "Holy #$@%", within the first few seconds when fed +60/-60. It loved it. Some other components were indifferent and the only benefit was the same as isolation. Apparently, I'm the only one to find components disagreeable to balanced AC but I think that's more of an indictment of the component.
Some have found even the minimal intrusion of an iso transformer to be a detraction. Not sure if they had double the continuous current capacity for their load, which is a good rule of thumb, or any other specific conditions. That's the deal with (any) transformers, they can be unpredictable when not accommodated properly. If you're dealing with 50 Hz, be sure the unit is rated for that.
For power, I prefer EI core as opposed to toroidal. This is 50 or 60 Hz only and the wide bandwidth, close coupling of toroids becomes a disadvantage. There's also DC sensitivity and saturation differences. The advantage of toroids is smaller, lighter packaging, local EMI, and resistance to mechanical hum due to closely packed windings. If it's going to sit in the room AND it's large capacity, toroid might be better under broad conditions.
Efficiency of transformers is usually around 90% but they also draw a minimum unloaded current, dependent on size, so there is a running cost penalty.