hi,
well i dont know what your other tank will be holding and i highly doubt it requires the effert and time that a discus tank needs, wc, feedings ect.. so as far as the placement for your discus tank, pick which will be easier to take care of for you... with frequent water changes and cleanings being the key to a healthy fish. just my 2 cents. hope its of any help to ya! o by the way, it should be a nice set up when its done!
nolan