A couple points of differentiation:
1) First-shot completion: Our system typically gets 90%+ of the questionnaire completed with no user involvement. I don't think RFPIO (or other RFP-focused platforms) do that.
2) Guidance & Support: Some of the stickiest parts of RFPs are the questions that are either WTF? or that you answer "No" to and determining how to manage that. Does it actually matter that you don't have a WAF (depends on the rest of your architecture)? Does it actually matter that you're still using TLS 1.1 (probably want to change that)? Should you fix those things? RFP systems don't help with that; ours does (largely because we've put a human in the loop).
What I've heard from our customers using those systems is that RFP systems help (after you've spend time on curation) with ~30-60% of questions. If the questionnaire is 200 questions, that still leaves you with somewhere on the order of 100 questions to answer.
Ultimately, RFPIO provides a software tool only; we're providing a software-enabled service.
The time your team spends on questionnaires is reflected in that.