I have multiple tanks (7 currently, a 115g, 90g, 70g, 33g, 29g, 20g and 10g) and with more than 2 I have always preferred having them together. I can sit in the middle and turn to any tank to view it; there is an advantage to this, when sitting quietly for long periods it is interesting what one can see in the way of fish interaction, that you might miss if in another room. So I have a "fish room" at the end of the house. It also makes maintenance easier; one morning a week I run the Python from the laundry sink into the fish room and do all the tanks. One cleanup.
The weight issue is very important. My house is a rancher style sitting on a concrete slab, so weight is not an issue. In a wood frame house with a basement, I would make the fishroom in the basement; this also makes it easier to keep tanks cooler in summer in a basement.