Yeah I don't know what you mean either.

If you let the water drain to one floor level below, then you'd need to spend energy pumping it back up, plus the height of the toilet. Installing a tank above the toilet, and pumping to it from the tub, would be "easier". That is, unless you're filling a 100 gallon tub daily. In that case, using an outdoor reservoir would be more suitable, and easier than pumping it up ~15' after draining to a basement. If you're looking at the "ease vs difficulty" of a one-time install, then you're not paying attention to the long term factors.