It depends if it is just UK to Dubai (only ~6 hours) or a connection further afield, whether it is a day or night flight and whether you need to be fresh when you arrive.
Whether or not it is value for money for you is very personal and depends if this is a ‘one in a lifetime’. The perks of extra baggage, fast lane past queues, lounges, better food / drinks and better service are all very nice but only really add a few 100 in value (compared with eating in an airport restaurant beforehand, paying for baggage etc.) For me, the benefit I would and have paid for is the lie-flat bed – it makes a huge difference on night flights or where you are changing numerous time zones. I would choose to travel longer / further in order to get a cheap business class seat flights >10 hours (west coast USA, Asia, Australasia) over a more direct route in economy, because sleeping well can stop the jet lag and basically gives you an extra day / few days not feeling groggy. But of course, what you consider ‘cheap’ business class depends on what you can afford.
If you don’t fly enough to get status / miles and understand the scheme, you will probably be much better off with a credit card earning cashback rather than frequent flyer miles. Some bits of schemes are good (e.g. short haul rewards on BA, if you live near London, and also within USA, Australia, Asia on partner airlines), they have all generally tightened up recently (getting reward availability in premium cabins on popular routes is very hard).