Verdict
Built from the measurements below
- Accuracy is too close to call: Inkling scored 66.2% and Step 5 Preview 63.8% on the same 80 questions, a gap within what chance alone could produce.
- Inkling is 3.8× cheaper per question as billed ($0.0012 vs $0.0047), reasoning tokens included.
- Inkling generates text 1.3× faster: 118 tokens per second against 93.
- Inkling starts answering sooner: 0.6 s to the first token, against 0.6 s for Step 5 Preview.
- Step 5 Preview accepts more context: 1M tokens against 524k.
Which should you choose?
Choose Inkling for the lower cost per correct answer ($0.0019 against $0.0074), faster streaming, a quicker first token and shorter outputs (about 228 tokens per question against 1,630). Choose Step 5 Preview for a 1M-token context window and more hosts to choose from on OpenRouter (4 against 1). The widest subject gap is in law: Inkling answered 4 of 6 correctly, Step 5 Preview 2 of 6. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.
Accuracy gap +2.5 points (z = 0.33). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.