FC Miles and Upgrades

I've been calcualting how much it would cost to go to HKG in July. I have 10,000 miles at the moment.
If I book PE plus buy 30,000 miles for a UC upgrade it costs a total of 1622.
If I book UC plus buy 5,000 miles for M+M it costs a total of 2026.
Is there a catch in either of these options?
If I book PE plus buy 30,000 miles for a UC upgrade it costs a total of 1622.
If I book UC plus buy 5,000 miles for M+M it costs a total of 2026.
Is there a catch in either of these options?