I have a 10' 4 wt that I use almost exclusively for nymphing. I think it's just about perfect, but my winter project is a 10' 3 wt that will probably replace it next year. It's a personal thing, but I believe the advantages of the 10 more than offset any "weight difference." I also know my first rod, a 9' 5 wt from a $100 beginners kit, including a reel and line, would tire me out a lot faster than my 5 wt Helios2 does today. My belief is, the weight question is only valid if you compare the 9' to the 10' version of the same make and model rod. Byron makes a good point, the longer rod is more difficult pack.

Cliff