IMO,
I have tried Seaguar, great line too expensive
I have tried Berkley big game; this stuff is ROPE! 20# big game is as thick as 40# fluorocarbon, and yes line diameter does matter when running spoons. (try this on your own, put that same spoon on two rods, one big game the other a thinner diameter line. Hold the two out and watch the difference, the spoon can only do what its physical limits are, a smaller diameter line cuts the water easier and allows for more water to hit the spoon causing more action; more action means more fish!)
I personally prefer 20# Berkley Vanish Fluorocarbon in the blue box, the Berkley gold I do not like
Seaguar Fluoro is $26.99 for 200 yds, Berkley Vanish is $15.49 for 250yds; HOWEVER having said that big game is half the price or less than those previously listed
I fish Lake Huron, we face a very clear clean lake with great depth visibility so stealth is key so fluoro is a must
I have fished Lake O and had 15fish days of 20#ers and no issues with 20#.
Again snubbers are a must, big game is mono and does stretch, fluorocarbon does stretch a slight bit but very little