Well, if you are planning on using the rod as a pitching or flipping rod, the extra two inches will allow you to use less effort to get your bait where you want it. I personally prefer a 6'8" over a 6'6" for pitching.
not sure of the purpose but wouldn't a little bit longer rod making moving line on the hook set better, and casting distance. the height of the person using the rod might have something to do with it also. I have a rod shortened from 7 to 6'8 and love it. sometimes the 7 footers are just to heavy to use all day.
6'8" rods are the higher dollar rod companies way of sperating themselves from the rest. A lot of St. Croix's rods you will notice are 6'8". I think it has it's advantages. I'd rather have it be 6'9" so you're inbetween 7' and 6'6". The 6'8" however gives you the best of both 7 and 6'6. The extra length gives you the longer casting and better accuracy compared to the 6'6". I feel that it has a better backbone for setting the hook and fishing in thicker weeds and folage compared to a 7'. So in a way yes the 6'8" is better than a 7 or 6'6" because you can have a little of both world with out having to have both a 6'6" and 7' setup
Most of my St. Croix rods are in the odd sizes & all of mine have the medium power & Xtra fast tips. I feel the size is not the key here but the tip action is where you'll fall in love.. trust me worth EVERY penny just ask the guy standing next to me on the Maumee River or the guys Perch jerken'
XF is the winner hands down & the casting models have plenty of ass behind them.
6'8 AND 7' rods are great rods for flipping,more sensitivity, it gives you more leverage when fish are giving you a fight, it also gives you better casting distance and hook sets are easier........I have mainly fished with a 6'6 baitcasting setup but after I bought a 6'8 and a 7'0 I have been using them alot more than my 6'6