If you're only getting $280 (SGD?) value out of 50,000 miles, then probably not even worth bothering with the program.

To the OP, there will be no benefit, particularly travelling in business class, of being a Krisflyer member, vs being a United member vs being a member of no FF program. So it then comes down to the value of the miles you earn (a "good business class ticket" probably is in the cheapest fare class, so probably earns 125% of the miles travelled in Krisflyer and 100% in Mileage Plus). If you have access to credit cards that earn Krisflyer miles it might be worth it, but a one off trip is probably not going to be worthwhile, particularly considering Krisflyer miles expire every 3 years after you earn them (hard expiry, nothing will keep them alive much longer than that other than paying a % of the miles to extend for 6 months).

Krisflyer is predominantly a useful program for those based in Singapore and SE Asia (particularly Indonesia) and perhaps to a lesser extent those based in Australia and India. And of course those based in the US that generate lots of miles through either large spending or credit card churn/promotions, to use on Suites bookings.

So it depends on where you are based, and what the length of the journey will be. But, for example a simple return from Europe to Singapore would barely be worthwhile.