When I took my 12 wpm morse test at Trusthorpe (Mablethorpe), I asked the examiner what speed they used commercially. He said they used 14 wpm as it was better to get it sent correctly and copied correctly first time. He said rhythm was an important part of sending.
14 wpm now seems a little slow; perhaps it is still more appropriate to passing an important message or indeed just having a chat. The requirements for making a successful SOTA QSO are somewhat different… one might say less onerous, but accuracy is still important. From an activator’s perspective, I find around 18 wpm to be optimal under the conditions that I often experience on a summit