I use Outlook.com for my primary email and I’ve had a few more outages than with Gmail but nothing I would consider major. The major issue is Outlook.com’s spam filtering is drastically worse than Gmail, I get so much spam that would be just so obvious to any rudimentary spam filter, I mark them as spam in Outlook.com, and the next day I get the exact same email again.
Maybe their spam filtering is worse, but they also block way more legitimate smaller mail servers for no good reasons. Every few months I have to send an appeal to them so that I can continue sending mails from my mail server. They claim that there were user complaints about spam but it's pretty much impossible. I think they just silently blacklist smaller mail servers periodically and hope that they can fight spam that way. Obviously they can't.
So if you want to be able to receive emails from smaller mail servers - don't switch to Microsoft.
