Re: Choosing my next rod
If your 5 weight is a 9 footer, I would suggest a gentle action 4 weight that is 7-8 feet. It will give you extra capability for small-stream fishing and delicate presentations. In contrast, a 9 foot 6 will give you a little extra casting power but will mostly duplicate what you can already do with your 5.
Ont he other hand, if your 5 weight has a softer action and/or is 8' 6" or less, you may find that a 9 foot 6 will give you more utility for long casts, windy days, and/or weighted rigs, while a 4 would do most of the things that your 5 already does.