I currently have 52,000 miles and I am about to fly business class GLA-DXB-HKG return and saw that it would cost me 50,000 miles to upgrade to First class for one leg.

The question is, is it worth using all my miles and if so, which leg is best to experience first?

I am on the early afternoon GLA flight and then 3am flight to HKG returning on the 6pm flight out of HKG and then early morning flight to GLA.

Any thoughts/opinions welcome?