What matters in a spring mattress is not the number of coils-- that's just marketing crapola. What matters is the wire gauge of the wire used in the coils. And the amount and quality of the padding on top of the springs-- which varies by thickness and type of filling. What a lot of folks like nowadays is real firm springs topped with real thick, fluffy padding. Like house framing-- basic great structure covered with layers of stuff for comfort and, finally, looks.
I think the "new" stuff is about magic memory foam. Me, I'm a springs girl, always will be.