Mac Studio M5 Ultra 256 GB vs Mac Studio M5 Ultra 512 GB
Verdict
- throughputThe Mac Studio M5 Ultra 256 GB delivers approximately 40% higher aggregate decode throughput across the 8 models both machines can run (geometric mean of the per-model ratios).
- capacityBoth machines run all 8 compared models, so this is a pure speed and cost decision rather than a capability one.
- costAt 8 hours a day, the Mac Studio M5 Ultra 256 GB has approximately 24% lower total monthly cost (€90 against €118), for a C corporation in United States (federal).
- evidenceEvery throughput figure in this comparison is estimated. Treat the ranking as indicative and the margins as unreliable.
- recommendationThe Mac Studio M5 Ultra 256 GB is both faster and cheaper to own here, so it is the straightforward choice unless you need something specific to the Mac Studio M5 Ultra 512 GB.
Every statement above is generated from the calculations on this page by fixed rules — no prose is written for individual comparisons. If the numbers change, the verdict changes with them.
Hardware
| Mac Studio M5 Ultra 256 GB | Mac Studio M5 Ultra 512 GB | |
|---|---|---|
| Price (NL, incl. VAT) | €8.647 | €11.350 |
| Memory | 256 GB | 512 GB |
| Memory bandwidth | 1,200 GB/s | 1,200 GB/s |
| Achieved bandwidth | 1,052 GB/s (88%) | 1,052 GB/s (88%) |
| Nominal power | 300 W | 310 W |
| Measured load power | 215 W | 225 W |
| Idle power | 13 W | 14 W |
| Architecture | unified memory | unified memory |
Model performance8 models run on both
GLM-5.3 FlashDeepSeek-V4 FlashHunyuan Hy3Qwen3 235B-A22BQwen3.8 Flash NextQwen3.5 122B-A10Bgpt-oss-120bQwen3-Coder 30B-A3B
| Model | Mac Studio M5 Ultra 256 GB | Mac Studio M5 Ultra 512 GB | Winner |
|---|---|---|---|
| GLM-5.3 Flash 321.323B (18B active) | ~62.1–89.3 t/s Q4_K_M | ~36.6–52.7 t/s Q8_0 | Mac Studio M5 Ultra 256 GB +70% |
| DeepSeek-V4 Flash 304.18B (13B active) | ~89.3–129 t/s MLX 4-bit | ~49.8–71.7 t/s Q8_0 | Mac Studio M5 Ultra 256 GB +79% |
| Hunyuan Hy3 298.786B (21B active) | ~57.7–83 t/s MLX 4-bit | ~31.6–45.4 t/s Q8_0 | Mac Studio M5 Ultra 256 GB +83% |
| Qwen3 235B-A22B 235.094B (22B active) | ~51.5–74.1 t/s Q4_K_M | ~30.2–43.5 t/s Q8_0 | Mac Studio M5 Ultra 256 GB +71% |
| Qwen3.8 Flash Next 180B (6B active) | ~162–233 t/s Q4_K_M | ~101–145 t/s Q8_0 | Mac Studio M5 Ultra 256 GB +60% |
| Qwen3.5 122B-A10B 125.086B (10B active) | ~63.6–91.6 t/s Q8_0 | ~63.6–91.6 t/s Q8_0 | Tie (0%) |
| gpt-oss-120b 116.829B (5.1B active) | ~203–293 t/s MXFP4 | ~203–293 t/s MXFP4 | Tie (0%) |
| Qwen3-Coder 30B-A3B 30.532B (3.3B active) | ~167–240 t/s Q8_0 | ~167–240 t/s Q8_0 | Tie (0%) |
Differences under 10% are reported as a tie: they are smaller than the spread between published benchmarks of the same configuration, so calling a winner would be false precision. Rows where a model fits on only one machine are decided by capacity, not speed.
Economics — United States (federal), C corporation, 8h/day
| Mac Studio M5 Ultra 256 GB | Mac Studio M5 Ultra 512 GB | |
|---|---|---|
| Purchase price estimate | $8,647 | $11,350 |
| Reclaimable VAT | $0 | $0 |
| Net cash at purchase | $8,647 | $11,350 |
| Monthly depreciation | $100.88 | $132.41 |
| Monthly electricity | $1.32 (9 kWh) | $1.38 (10 kWh) |
| Tax programme | §179 100.0% | §179 100.0% |
| Tax-programme benefit | $1,816 | $2,383 |
| Monthly economic cost | $90.39 | $118.37 |
| Total over 5 years | $5,424 | $7,102 |
Tax assumptions last verified 2026-09-07. Federal planning estimate only, not tax advice. State and local income tax, sales/use tax and incentives are excluded. It assumes 100% business use, a Section 179 election, enough business income to use it, and that the full annual limit remains available.