Yes, a longer rod helps with dries too. Casting is a bit easier, especially for a beginner, as it helps keep your backcast high. That's also a plus for low lying streamside vegetation, like grass. Mends are a bit easier. It's easier to lift that line over cross currents to prevent drag. Hooksets a bit higher. Longer rods are simply better fishing tools, provided you have the room to handle em. That's why your big river spey rods and such are more like 15 feet!!!!
Of course, if you're trying to maneuver a long rod through brush to get to the stream or to move up to that next hole, it's a pain. And if you have an overhead canopy of trees, you'll find that keeping your line high isn't all it's cracked up to be, plus you'll get PO'd when you smack that rod tip on that branch.
So there are trade-offs. And we really can't tell you what will work best for you, only you know the situation where you fish. All I can say is that in PA, where the standard fishermen typically fishes medium sized, semi-open streams, a 9' 5wt is considered the standard. It's most people's first real rod and remains the workhorse, forever really.
Though ryguy has a good point. After we got our 9' 5wts, most of us branch out into specialist rods. If you're gonna do some small stream fishing, something around 7' or 7'6" is ideal, and even the experts will argue whether that should be a 2 wt or a 5 wt or something in between. If you have eyes on smallmouth bass or steelies, a 10' 7 wt is nice. And neither of those rods may be ideal in your normal fishing situation, but they'll both do just fine in a backup role.
Then again, if you don't like your workhorse rod, then get something similar and call it an upgrade, the old rod becomes the backup. The comparison to guns is a good one. A 30-06 or a .270 will work for just about anything if you want to buy one gun and be done with it. They're perhaps perfect for elk and bear, but for whitetails and groundhog I'd prefer a .243, and for squirrels a .22. For most, a 30-06 might be your first gun, but most wouldn't buy a 2nd, might as well get something else that will be your 1st choice for something.