Price is always a factor in my world. If price wasn’t a factor, “value” would be relatively meaningless. They’re both “good” headphones, and the differences they offer are down to subjective tastes of personal opinion, and whether or not you need the features each has. The Arctis Pro has a slightly more clinical, laid back sound, and I moderately prefer the sound of the M50X.
But I don’t hate either of them at all.
The only world in which the Arctis Pro + GameDAC presents a totally good value is if you’re starting from scratch and need exactly everything that the package includes in the box. It means you need an RGB gaming headset, a good microphone, and a hi-res DAC that only connects to this headset and offers DTS Headphone X 2.0 on a PC.
If that doesn’t describe you…then the M50X is a much better value, though again, it doesn’t sound “better” so much as “different.” In fact, it sounds nigh-identical to the M50’s you already own. It’s much cheaper than even the base Arctis Pro model, it’s able to connect to a litany of DAC/amp combos, game consoles, and other devices, and it leaves the door open for you to provide your own mic…which can be a little cumbersome. But with the money you save you could easily buy a lapel mic and a basic amp, if you want.
The M50X doesn’t really have a big soundstage, however. If you want that in a closed-back headphone, you’ll need something like the DT770 Pro.
Otherwise, I’d say you should look into open back headphones, especially if most of your listening happens at home. The SHP9500 is a good starting point, as is the Sennheiser 500 series, and if you love treble you’ll love the DT990 Pro.
If you need an open gaming headset with built-in mic…your options are pretty limited. Sennheiser just introduced the GSP 500 and they have their vaunted Game One as well…though I think those models are probably a bit too expensive. The Astro A40 and A50 use an open design…but they’re also quite pricey.