[Q]

Here was my key deciding factor for migrating my wife from Hotmail a few months ago.

Within the last half year, both Hotmail and Gmail have both had down-times where user data was lost.

Gmail recovered from tape. Hotmail lost TONS of messages including a nice handful from two of my wife's accounts. Gmail communicated the issue clearly and provided status updates. Hotmail did not.

Remember to archive your messages offline once and a while, too. You're going to get zero support from either company if they lose your messages or your account is compromised since you're not a paying customer.