Seaguar Grand Max FX Tippet
So if you compare the charts in relation to the diameter to the lb test, you will quickly see that with the more expensive tippet the diameter to lb test ratio is much better. The InvizX 4lb test is .007" diameter while the Grand Max FX tippet .007" diameter is 7 lb test. For the same diameter you are getting 3 lb more strength and that is what your paying for. As you move down the chart you see that the 17 lb InvizX has a diameter of .015" while the Grand Max FX tippet is over 25 lb test in the same .015" diameter.
Now personally I don't think it makes that much of a difference when it come to warm water or big game fishing when you are throwing large flies. However I do think it makes a difference when you are presenting small flies like #18, #20's and even smaller #22,#24, and #26 midges, BWO, and what not to large trout like on the San Juan. The San Juan and a number of other great trout streams across the country are known for being very technical fisheries were you typically throw small flies to relatively large fish. The smaller the diameter your tippet is the better these small flies can be presented naturally and the added lb test strength will result in fewer break offs and more fish to the net.
Just something to consider the next time your at the flyshop picking up some tippet.