Being honest K28,there's not much difference between most 11ft 6 ins switch rods and most 13fters, it usually boils down to 18" of carbon. £ to a p they'll chuck the same lines near enough the same distance and you could be using them in near enough the same restricted space's.
Where I would say there is an advantage is going to lighter lines, exploiting a better presentation of smaller flee's off lighter nylons.However you could also utilise lighter lined small 12ft double handers too!.
There's a world of choice out there and it can be bewildering!.
I could tell you this for certain!, not much point in buying an 11ft 6ins. 8/9 weight switch when you've an 8 weight 13fter, thats for certain, but a 6/7 weight 11ft trout rated switch could put fish on the bank for you in times of low water.
I've 3 switch rods, an 11ft 3 ins 6 weight Airflo, the same rod in 7 weight and a Sage One 8 weight. Each one subtly different and exploitable in certain circumstances.The Two Airflo's are Trout rated and are a godsend in low clear water, the Sage while Salmon rated and far "beefier" is pretty much the same as my 13ft 8/9 LPXe!.
More honesty now!, I've a 12ft 6ins. 7 weight rod too, that really works well on medium rivers esp. in lower summer levels!.
Maybe you know the answer to your own question?, just a couple of lines of thought there for you.
Feel free to ask any time, happy to help.If we're close welcome to try my kit out see what you think before splashing any cash.
Pedro.