It's effective (that has been proven in independent tests) and is lightweight so doesn't slow your computer down, so it compares to AVG very well.
You can still use malwarebytes with MSE and I would recommend doing so, they live happily together and malwarebytes is still the best antimalware solution IMO.
I get continual messages for wanting to do an upgrade and then it doesnt go through with the message you are using a WE with a different build flavour. However when I look at the history, it has worked......its bugging me somewhat and Microsoft have been useless.....
I have found that trying to update the client itself from the Help > Check for software updates - menu to be unsuccessful. However, if you uninstall the old client and re-install this new one, you will have the latest software build. Charcoal background instead of a blue one. Few differences except for newer engine and some more customisable options.