The difference was that MS was actively working to make sure that no other OS or Browser could succeed, intentionally breaking stuff, "DOS ain't done until Lotus won't run", using contract law (Gate's family were lawyers and he got their monopoly through lawyering rather then having the best product) to stop manufacturers from carrying any other OS, using undocumented API to make sure their offerings worked way better then the competition and forcing IE down the throats of users as well as breaking standards left, right and centre.
While Google has grown too big and since going public, are much more evil then they were, they're still easy to avoid. No paying Google every time you upgrade your hardware like I found myself doing with MS. Fairly easy to switch. My phone is easy to get the boot loader unlocked by going to the manufacturers website, clicking a bunch of warnings and getting the unlock code. I remember installing Win95 on a computer with OS/2 on it. Happily installed with no activation code and at the end informed you that all the stuff on your OS/2 partition was now gone along with your work, rather then saying to go to fdisk and make Bootmanager the active partition.
It was due to MS putting so much effort into leveraging their desktop monopoly to monopolize the web that they deserved to be broken up. When Google starts the same shit, then they should be broken up. Right now I use them for some stuff because they have a better product, just like why I started using them in the beginning. I've tried Bing for search and it's crap for what I was searching.