I haven’t been following the pricing on these lately, but the 3520C is right at $4,400 - 4,500 and at least a couple times a year that gets discounted by 15 to 20% or other promotional pricing.
So, for $1,000 more, you get a more robust and refined lathe with a warranty and fewer surprises.
The electronics in the 3520B can have issues. There are well established fixes out there, but they still cost a bit.
Historically, I’m pretty sure Powermatic does Black Friday/ Cyber Monday pricing. So if you’re not in a hurry and the extra $1,000 for the 3520C is a possibility, you may see that pricing sooner than later.
BTW, we’ve had this discussion in the past. A few years back, the sale price for the 3520B was $2,500 with the bed extension. I think there were threads on this forum.