I have four trout-speys laying around the house.
A 93 bamboo (that I like with about 190 grains)
A 10 graphite with a 200-230 grain window.
A 12 graphite with a 240-300 grain window.
A 12 graphite with a 210- 265 grain window.
They are normally used on very different streams. Last year I used the bamboo on the Madison River in YNP and just below the lakes, but found it a bit short for some of the casts I needed to make at times (70ft). I would have been better off with the 12ft 3/4wt. The 10ft 2/3wt and the 12ft 3/4wt are the mainstays. The 10fter pulls warm water duties too. I can use the 12ft 3/4wt on tailwaters during the winter in Arkansas to go along with its time in WY/MT. However, the 12ft 2/3wt may see a bunch of time next year, hopefully in OR this Spring and MT in the Fall.
I like the little 10ft for its lightness, but if the stream is of any size the 12ft is nicer for its mending abilities. I hope to add a 109 3/4wt bamboo in the next year.
Ive made a few short bamboo (9ft) micro-Skagit rods for some friends (all around 200-230 grains), and Im being asked to modify more 9ft 5/6wts graphite rods to two handed rods. My seven-year-old daughter will start using a 10ft 2/3wt this winter/spring.
Im not sure about going over 12ft for the trout stuff, especially in the 2/3/4wt realm. I would be concerned that the lower section would become too stiff for a 200/250 grain rod to allow the fish to be fun.
I guess my very long winded and rambling answer it depends on the size of the stream and size of fish.