Have a hardtail and softail frame, both lovley, and both light. Recently bodged the softail into a singlespeed and have quite enjoyed the experience. Find it's a the chosen mount for a short, fast blast. The geared bike for longer rides.

Musing as to which frame is the best option for SS – I know it's prob marginal difference and personal prefernce, but just interested on any thoughts?

Hardtail.

Eventually you'll spend so little time in the saddle that suspension is just more weight to drag around.