That may be fine for road based riding (road, TT, Tri), but with a MTB in the mix, a pedal-based power meter is a non-starter. There’s no way that using a Vector, Assioma, or P1/2 pedal PM would be a safe or good option on MTB. It is too fragile to handle rock strikes, and the cleats will clog in mud/dirt, or be shredded with any off-bike hiking or running.
Power meter variation is not impossible to look at or deal with. It is a better compromise than shoe-horning road pedals into MTB use.
I’d also like to publicly complain that I can’t seem to get a power meter with 46/36 crank rings so I’m going to have to burn some money. I currently have a Quarq Elsa R which is 130BCD so I can only fit 46/39 and that’s fine for CX but miserable in high elevation mountains, and it’s also Ant+ with no Bluetooth, so it won’t connect to my phone without an Ant+ dongle but that will then burn my battery, lol. This is my #1 first world problem.
Get one of these and get a 46/36 installed from the factory on any of the options: https://power2max.cc/collections/ngeco-road-powermeter
$600 for that meter and I still have to pick-up crank arms and rings so well over $1000. I’ll survive though.
You can get a rival crank for $130 or just buy one of the FSA options with arms for $490 /shrug
4iii is cheaper than Stages and more accurate too. And don’t buy anything from China – quality and accuracy will not be there plus no way to return them.
lol @ Rival or FSA boat-anchor cranks. I’ll just wait for the next bonus or gold brick I find to do an Ultegra crank.
This thread makes me feel old, I remember cyling before SRM when we measured our training in hours 
…then SRM came along but only the pros used them because they were so expensive …and here were are today complaining about hoe ‘expensive’ they are.
Building a good PM that works in the real world is not easy (Garmin Vectors anyone?) so I for one am grateful we have a great choice and can pick up a good PM for a few hundred bucks/euro…
For what its worth, I agree with you. I would love to have a power meter but simply can’t justify the money. Right now a carbon fiber wheel set is more attractive. One overpriced purchase at a time!
In my not very humble opinion a PM would be a better buy over all other ‘extra’ purchases if you are serious about training and improving. Plus it would cost a lot less than a good pair of carbon wheels
Does your opinion hold if one has access to an indoor bike with a PM in the gym but is considering also getting one for the MTB?
Okay, but I am using estimated power on the trainer so is that not good enough? Once I get outside it will be a problem. Power is out the window in that case, so I see your point.
In the end it’s a question of priorities (including real life!) and on reflection, also where you are in development as a rider, so I’m now going to contradict myself a bit! …for example if you were say a junior or very new to cycling I would encourage you first to ride and train on RPE to get to know your body and how it feels/reacts. If then you want to take it further and try to really develop yourself then I would say a PM will be the best bang for your buck to help you get there. On the other hand if you just want to enjoy riding without performance goals then get the wheels cos your bike would look sweet and you’d feel great 
Hey, I’m a kettle of contradiction. No worries. Believe me, I’ve struggled with this exact question: PM vs. Wheels. If I were a young rider (not!) that wanted to compete then definitely. In my case, older and just trying to snag KOMs and get fit, not so sure. A PM might still be the best bet but, I still want to go out and just tool around. I love riding and just like banging around on the bike. For me, TR is my only hope (as Princess Leia once said to a droid) for eking out some fitness before I turn to dust. Its a better option than randomly riding around, which is what I’ve been doing for 3 years. Besides, the wheels are so sexy.
So not true in many cases. Those being if someone has a very non-aero aluminum wheel and moves to a mid to deep section carbon. There is real speed to be had, well and truly above the “black-bling”.
From DC rainmaker, taken directly from here
XCADEY POWER METER
This is a left crank arm power meter similar to the design of Stages. The price has been appealing for many people because it’s sub-$200. Unfortunately, I haven’t seen any evidence that this Chinese power meter is at all accurate. From the company’s own eBay pages (which is where they sell it), they use power meter comparison graphs that quite honestly look horrible. The power is often wrong by upwards of 80w (compared to an SRM and PowerTap hub data they provide), and in fact it’s virtually never aligned properly. You’d be far better off looking at a non-DFPM such as PowerPod down lower for roughly the same price. Or spending a bit more on something like the WatTeam single-sided unit. While some have asked for a review, I’m honestly hesitant to waste time on a product that the company can’t even bother to cherry pick the best possible data to publish on their sales/marketing pages. What’s the non-good data look like if this is the best they have?
Advantages: It’s still at least a Shimano crank arm even if it doesn’t provide accurate power numbers.
Disadvantages: It doesn’t appear to provide accurate power numbers.
Would I buy it: Nope.