Hi Clayton. I did the Frances this past November and the Primitivo in January - they're wildly different - from ladnscape to trail conditions to infrastructure. Those differences will appeal to some and not to others.
For me the Primitvio is my least favorite of my caminos. I have super nice memories of locals met, of large Asturian dogs angrily woofing in the darkness and then appearing out of nowhere only to start wagging tails for cuddles ( not the outcome I expected
But the actual walking - was the least enjoyable of my caminos (I felt it poorly designed w/ excessive busy road walking, poor signage, some sketchy sections that require care for the beginner - and overall wasn't the beautiful mountain landscape I'd expected. (for context Im in mountains often- and this was January - so solo walking, shorter days, very limited options for food, water and accommodation).
In general if you have just moderate outdoor experience and good condition, you'll be find it an easy to comfotable go. For someone without,you'll get stronger enroute as you would with any camino - but unlike the Frances, the Primitivo goes up or down...there's vey little level. So that improvement needs to ramp up a bit quicker
It's considered the most difficult camino for a reason...
For a first camino (depending on your condition) I wouldn't recommend it. In January I met only two other walkers- and this was thier first.. For one, an ordeal almost from the start (we stayed in contact throughout by text).and they needed to skip the middle sections altogether. The other was walking well into the night to finish their stages (which was super impressive - finding her route with headlamp through the more mountainous stages). So it was challenging - but I know both of them were so glad to have done it.
If you have an inkling to do the Frances, then I'd say go with that. But the takeaway here - for anyone doing their first camino - is to listen to your SELF - in the end it's your camino, not mine or anyone else's and there will be reason you chose it.
Wishing you a wonderful camino!
buen camino!