They are very different programs that work for different types of business. I use both, depending on whatever is most suitable for the client. It would help to know what sort of business you are in, so that others could offer some more specific thoughts.

Xero is geared up for automation - you can email up an attachment then allocate it in Xero. Bank feeds pull in automatically and the software suggests which invoice would be paid for each line on the bank statement. You can attachments to all transactions, which is a big advantage.

Xero is much better for sharing at remote locations, although I do manage this OK with Sage but with some bumps.

It is clumsy and slow for keying in, though - no shortcut keys and the screen is taken up with too many boxes and white space so you only see a few transactions on each screen. Also, you can't back it up. Of course Xero itself is secure, but I often import large sets of data and on Sage I would always back up first in case it goes wrong. If it goes wrong in Xero you have to unpick it.

Many people love Xero reports but you will never get near the flexibility of Sage report designer (if that's important to you). Also, I find Sage Transactions list invaluable but Xero doesn't have that same level of transparency. It is disturbingly easy to "lose" a transaction in Xero if you're not familiar with it, so I'd be cautious of letting junior staff loose on it without a lot of supervision.