What are the advantages/disadvantages apart from the obvious loss of one gear in the middle somewhere if both drivetrains start and end on the same size cogs
1×11 has extra gearing range, that's good. But you have to know, a 11 speed chain is thinner than 10 speed, so you should pay more attention to gear tuning. Spare parts for 1×11 are less common and more expensive. I don't know exactly, but I suspect that 11 speed transmission will be less reliable. In my bike store working experience, a SRAM GX group offers a rear derailleur that has a stronger spring; your chain will stay on the sprocket in most situations, but shifting would require more force.