When comparing BlueStacks vs ARC Welder, the Slant community recommends ARC Welder for most people. In the question“What are the best ways to run/emulate Android on a PC?” ARC Welder is ranked 5th while BlueStacks is ranked 7th. The most important reason people chose ARC Welder is:
Even though it's a developer preview, it's likely to evolve quickly as Google is developing it. Since Google is also behind Android, it makes sense to use a more official way of running APK. If they don't work, you may check with the developer so it may eventually work.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Easy to use and set up
For end users who are not developers, Bluestacks is perfect for the simple reason that it is just one click install, one just need to download the package and install it on windows or Mac to start accessing games and apps. It is just simple!
Pro Designed with gaming in mind
Pro Creates shortcuts for Android apps
A folder on the desktop with shortcuts to apps will be created. Opening a shortcut will start up BlueStacks and run the selected app.
Pro Decent performance
Pro No need to register in order to download and install
Only a Google account is needed, which is the same as setting up an Android phone.
Pro Can install apps from Stores and from APK files
Installing apps from APK files is important for developing purposes.
Pro Can run multiple instances
Now, running multiple instances of BlueStacks is possible even with different Google Accounts.
Pro Can transfer files between BlueStacks and Windows host
There are shared folders for this purpose.
Pro Built-in search allows quickly looking up and installing apps
Pro You can use BlueStack tweaker (portable), then you can access root and easily transfer files
You can not only transfer from Windows to Android storage (from BlueStack tweaker), but you can also delete or rename a file from it and also access themes and other options.
Pro Developed by Google
Even though it's a developer preview, it's likely to evolve quickly as Google is developing it. Since Google is also behind Android, it makes sense to use a more official way of running APK. If they don't work, you may check with the developer so it may eventually work.
Pro Cross-platform
Works on Chrome 41+ on Windows, Mac, Chrome OS and Linux.
Pro Allows running apps in a Chrome web browser
It installs as a Chrome App and runs on most operating systems (Windows, Mac, Linux, Chrome OS), even thought x86 support will be put in maintenance mode soon.
Cons
Con Does not run on Linux
Only for Windows and Mac OSX.
Con Default home screen can not be customized and lags a lot
Con Default launcher hides almost all normal Android functionality
The default launcher acts like a portal to launch games and not much else. If you're looking for a stock setup without much tweaking, look elsewhere.
Con Has bloatware and popup ads on free plan
You have to pay to remove both bloatware and popup ads.
Con Discontinued
Discontinued after December 2020.
Con Not all Google Play services are yet supported
ARC Welder supports OAuth2, Google Cloud Messaging , Google+ sign-in, Maps, Location, and Ads APIs from Google Play services.

Con Only supports "arm" apk files
"x86" apk files don't work as of 20150422.
Con Keyboard input is spotty
Con No accelerometer emulation
Con Orientation mode has to be selected before running the app
Con A single app can be loaded at a time
