I have one tank (60g cube) with a mixed background of vallisnaria behind the driftwood in one corner and some stems in the middle and a sword in the other corner. This tank has a few fish that are prone to dislodging things, so I want mostly plants that will root well and stay put.
My 30g cube tank has stems (unknown species, I think it's some type of myrio) and really tall narrow-leaf java fern in back. This tank has a lot of cryptocoryne and other low to medium light plants because the light isn't as good. It's also a somewhat deep footprint relative to height, so I wanted tall, narrow stuff that would give the feeling of the space continuing beyond.
The 20-tall that I'm re-scaping now is getting a clean uniform background of pearlweed along the rear wall, but I have rotala in the midground. It's a nano-fish tank, and I am trying to use some forced perspective with the size and shape of the plant leaves to make the tank seem larger and to provide a sense of scale with the tiny fish.
Things I consider when choosing plants are what sort of light is available, how different plants will look with the hardscape I've chosen, what kinds of fish are going in the tank, and what kind of feel I'm shooting for in the layout.
I've grown several species of rotala, and pretty much all of them do insist on decent lighting to keep their color.
One of my favorite mixed-rotala looks is an off-center cluster of wallichi flanked by two different colors (like a super bright pink on one side and an orange on the other). This can be really stunning if a few ludwigia are clumped in, like red mini and ovalis, and then a really green stem is tucked in to crank up the contrast. That look requires a lot of maintenance and attention to the tank though, and some people want to spend more time just enjoying their tank than working at it (and others really enjoy tinkering with it, and don't think of that as "work", which is equally valid).
Go with what makes you happy, and what will require a maintenance schedule you're going to be comfortable committing to.