Go with 2 tanks and let us know what happens
If the sunlight (or room light) is mostly from the top then the lid and light over the tank will block out a lot of it, and this will not add much light to the tank. I have one tank directly under a skylight, and use a glass lid and just one light fixture, so half the top area is glass to let in the light from the skylight.
If the sunlight can come in from the side (back, front) of the tank then this is going to help more than if the light is at the top, but cannot enter the tank.
If you (or a friend) does any photography, and has a meter, I would set up the tank (dry) in both locations, and check the light levels in various places in the tank. Go with the brightest location.