Fast DDR4 beats slow DDR5 for upgrades.

Usually. If you’re on a budget and upgrading an existing system (say, from 2666MHz DDR4), spending extra on entry-level DDR5 is a waste. A kit of DDR4-3600 CL16 will outperform DDR5-4800 CL40 in most real-world tasks because the latency is dramatically lower. The bandwidth advantage of DDR5 doesn’t kick in until you go faster – like 6000MHz CL30 or better – and that costs real money.

The problem with cheap DDR5 is that the timings are loose and the frequency is low. You’re paying a premium for the slot and the motherboard, but the actual performance is usually worse than good DDR4. In gaming, especially, the latency penalty eats any raw bandwidth gains. You often see DDR4-3600 beating DDR5-4800 in frame rates.

If you’re building a completely new system on a modern platform (Intel 12th gen+ or AMD Ryzen 7000+) that requires DDR5, then obviously you have no choice. But if the question is “should I upgrade my current DDR4 board to fast DDR4, or buy a whole new board and DDR5?” – upgrade the RAM, not the platform. Save the platform purchase for later when DDR5 is faster and cheaper.

Don’t pay extra for a worse experience.