AWS m6i.4xlargevsAWS m8gb.4xlarge

m6i.4xlarge pairs 16 vCPUs with 64GB of RAM at $0.7680/hr On-Demand (about $553/mo at 24×7). m8gb.4xlarge pairs 16 vCPUs with 64GB at $1.1640/hr (~$838/mo). m6i.4xlarge is 52% cheaper per hour than m8gb.4xlarge ($0.3960/hr gap).

These are different generations of the same series. **m8gb.4xlarge** is the newer generation, and AWS's pattern across generations is fairly consistent: ~10–15% better single-thread, 15–30% better multi-core, and similar or modestly higher per-hour pricing — so the price/performance per dollar usually improves with each generation. **m6i.4xlarge** is still available and still works (AWS doesn't retire instance types quickly), but for new workloads the newer generation is typically the better default unless you have a specific reason to pin to the older AMI or there's a meaningful regional pricing advantage today.

On raw price-per-performance, the two are m6i.4xlarge delivers ~35% more single-thread Sysbench score per dollar (3878 vs 2866 points per $1/hr). That's the cleanest signal we have for "which one runs your workload faster per dollar," but it only matters if your workload is single-thread-bound; for parallel workloads the multi-core scores (24759 vs 53169) are what to weigh. Spot pricing flips many of these comparisons — when m6i.4xlarge drops to $0.2722/hr and m8gb.4xlarge drops to $0.3433/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick m6i.4xlarge when your workload is closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). Pick m8gb.4xlarge when it's closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). When neither side is obviously right, the cheaper hourly rate usually wins for fault-tolerant batch workloads, while the higher single-core score usually wins for latency-sensitive web traffic. The regional pricing tables linked from each instance page below show where each is currently cheapest — sometimes a >20% regional gap flips the comparison entirely.