This question has no answer, since "best" is very opinionated. Best for your buck isn't any better, since to some people 8Cr13MoV is just not adequate steel at any cost, whereas to some the value line is an unbeatable value. It also greatly depends on what you expect out of size and materials. Some people see FRN simply as another kind of plastic, while others see it as a high performance handle material.
That said, i'd have to say the ZDP Delica is an amazing value for the steel you get for the price you can get it in if you shop around and catch a deal. I got one for $50, which is insane for ZDP. On the other hand, I paid $220 for my 20CP Para 2, and i feel that was a bargain for the steel it has. It's all about what you want and expect to get for the money.
I'm going to say other than the Para, the sage 1 is a knife i think bond would carry, tough as nails but sexy. The delica/ endura family no matter what steel its in is like the Glock of the knife world, frn, vg10, no frills but they work harder than you would think. the last i would say is the gayle bradly, like the sage 1 but bigger and badder with a really cool steel.
I'd say the best value for the money Spyderco I have is the Manix 2XL. The length of the blade, quality and grind of the steel and strength of the lock all for under $90 retail is at the top of the list.
For their value folders the Resilience is the best $40 folder I own...