Re: Choosing my next rod
If you plan to use it as a kind of back up, you probably will be happier with the 6 wt.
My 4 weights are purely for pleasure, and as such I fish them every chance I get. In fact, I've fished a 4 weight on every trip in the last 4 years. I like throwing medium to smallish dries on small creeks or even on lakes. I even toss hopper/dropper rigs with my 4 wts.
In my opinion, 4 weights are 3 weights that you can cast in windier conditions, and cast more kinds and sizes of flies. For example, I can cast my 3 wt. in winds up to around 10 mph, after that it gets ugly. My 4 wt. can handle up to 15 or so (this may vary depending on brands, lengths, lines, techniques, etc., but that's another question). So, many days that I can't unlimber the 3 wt., I can still fish my 4. And it's lighter, has a more moderate casting action than either of my 5 weights, which makes casting more enjoyable for me.
It might be easier to discuss what a 4 weight won't do, or at least what it doesn't like to do. In a word, heavy. Heavy lines, heavy/wind resistant flies, rigs, split shots, etc. are not what 4 weights are about, in general. You can make some of them cast these kinds of things, but it'll probably be a struggle. In other words, not fun.
anyway, hope that helps.
"Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark