Pedaling asymmetry is a real thing, and it's a real thing that varies with your cadence, your power output, and your level of fatigue. For many people, the asymmetry is small and not very variable. For some, it's large and variable. The thing is, almost no one knows which group they're in ahead of time. Some people think that if they don't know, they can safely assume that they're pretty even and that it doesn't vary much with cadence, power, or fatigue. Others think that if their friends (or friends of friends) are pretty even, then they must be, too. You might be lucky in this way, and if there were a large difference in cost between single and "dual" sided power meters, that might be a good bet to make.

It also turns out there are accuracy and consistency differences between meters but, frankly, most people don't do things that require much accuracy or consistency so they don't notice it. That's because most people only use their power meters for training their FTP, and training FTP is one of the *least* demanding things you can do with a power meter. Nonetheless, sometimes a few people do have issues (like, "why is my power different on this other device? Which one should I trust?" or "I just bought a new power meter, and it doesn't agree with the old one"), and we generally buy power meters to help answer questions and resolve problems, not to raise new ones. Once again, if there were a large difference in cost, this might still be a good bet.

However, right now, a Power Tap G3 hub with a perfectly acceptable DT Swiss rim is $500; if you have the right crank, you can get a Power Tap C1 chainring meter for $350. Both measure total ("dual-sided") power. Both are either cheaper or the same price as single-sided cranks or single-sided pedals; for example, right now the 105 version of the Stages costs $530. With the hub, you don't need an extra speed sensor. Depending on the rear wheel you currently have, the PT hub can actually weigh less than your current setup (especially if you're currently riding with a separate speed and/or cadence sensor).

With the current pricing on the Power Taps, you can have accuracy should you ever need it and still save money. People think that swapping pedals or a crank between bikes is easy, but swapping a wheel is even easier. The only real disadvantage of the PT wheel that I can think of is if you frequently travel between places where you want to ride a bike and you want power data for those rides. It's a lot easier to stick pedals or a single-sided crank into your bags than a wheel. That's a specific use case that not many people face. If you have a setup that is compatible with the C1 chainring, that'd be an even better deal.

Here's a plot from a paper published last year (2017) that compares accuracy ("trueness") and precision ("consistency") of power meters.