This is easy, Single = low cost (typically) and normally consistent data, if you are using this with training programs, it doesn't matter if there is a left right difference, it just matters that you always have that left right difference. The downside, of course, is it will be hard to relate and compare your data, use services such as best bike split, or switch to a different power meter like a smart trainer.

Double = high cost (except G3 hub, C1 chainring, and Power2maxNeco) accuracy + consistency.

So, if you only intend on training with that power meter for the next couple of years the cheapest possible, proven consistent (like stages with built in temperature drift control), single leg power meter will work exactly as good as a double.

If you like to hop between your power meter and a smart trainer, or multiple bikes with different power meters (think dirt and road, most power meters are usually not swap-able between them), or want in-depth comparative analysis against other people with double power meters, a double will likely better suit you.