I disagree. The feel of the 850s is great, but browsing is a pain in the ass. If you use them with SSL, they act exactly like they do with a USB stick with every feature perfectly emulated and great resolution, but you can use your laptop to browse and you get visible waveforms. The 400s on the other hand feel cheap and have jogwheels no better than a £200 controller. If you want the feel of a full size CDJ but don't have the cash to get the browsing abilities of a 2000 or Nexus, 850s with HID + software is a good solution.
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