Only you can decide what you like. Remember that you can create up to 3 aliases, so if you change your mind later it's not a disaster.
Note though that setting up client-based access to iCloud contacts and calendars on non-Apple devices is a bit of a pain, since Apple doesn't officially publish the CalDav/CardDav URLs and it doesn't work with some clients for some reason (e.g. Thunderbird with Sogo plugin stopped working a while ago). On Windows you might need Outlook, which is the only client supported by the Windows version of the iCloud app.
And iCloud actually offers 2-step authentication in most countries. I'd strongly recommend to use it.
Just know that you will be able to receive emails to william.h.gates@mac.com and william.h.gates@me.com as well as the @icloud.com domain. This has completely ruined a super awesome email address I used to have, First Initial, Middle Initial, Last Initial (FML@mac.com), as every idiot in the world with the same 3 initials presumed it was their email address. I ended up getting credit card and cell phone bills from the UK, a car payment email from France, and the social network signups of a 13 year old boy in Louisiana. Needless to say I ended up just not using that email address anymore because it was a problem that was impossible to correct.
