Which Groupset?

I was thinking about this and isn't the best way to choose a groupset to buy the most reliable and cheapest one you can afford?

Reduced weight has an actual performance benefit in a specific scenario like a hill climb where cycling is all about power to weight ratio, but weight weenie wheels and ultra light kit will lose all your time gains on the descent on the other side and the flat ride to the finish. No?

Yes 100%