[West O'5]

Imho a 4wt is slightly more versatile for various conditions(wind/bigger water/larger flies/weighted flies etc) and plenty sporting feel for pan size trout thru to 20”ers......heck when I started flyfishing 35+ years ago I had ONE flyrod,a 7wt 8’6” Fenwick Eagle that I used for everything from Atlantic Salmon to Great Lakes Steelhead to pan size brookies to trolling streamers for ice out Lakers and landlocked Atlantics....yes I was overgunned for the brookies but had a blast regardless.
That said,I can’t think of any legit reason to buy a 3wt over a 4wt unless you just want to witness 8” trout put a deep bend in’er?
Also agree with previous suggestions of overlining the rod by a line weight or 2...not just for wind,but for tiny streams it helps load the rod when you are fishing a short line wether false casting or roll casting...wutever...ie;your 4wt rod is designed to load with 30’ of 4wt line beyond the tip.
Fishing short on small streams it’s rare that you will ever have more then 20’ of flyline beyond the tip...overlining compensates for this.
Also imho there is zero benefit to buying relatively short flyrods;ie;6’6”-7’6” 3wts etc.
Granted,yes they are marketed as small stream/brush choked/Creek rods.....I’ve fallen for the marketing hype as well in years past....but it’s been my experience that I much prefer 8’ minimum and even 9 footers on the tiniest of creeks.Ive found on these tiny creeks I’m rarely ever actually casting anyhow other then a short roll cast,and often as not I’m merely “reaching” to swing a bugger/streamer/flymph,or dapping a dry etc.The longer rod I’ve found gives me much better reach to manipulate presentation and mending.The only advantage I’ve e er found to sub 8’ flyrods is a bit easier bushwhacking without takking the rod down/zero advantage and actually a hinderance when it comes to actual fishing and presentation imho.....I no longer own any flyrods <8’.