Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
I would think that the 250 would be easier than the 30 especially if the 30 has a walk-through transom. No telling what kind of transom mods would need to be made with those. An older 30 would be much easier but you'd need to get a custom make rudder, pintals & gudgeons.
If you are cruising I'd stick with the wheel. Spend the money on a good auto-pilot.
I know you didn't ask for opinions, but I'll add mine anyway... Having sailed a little on a C-30 with a tiller, and more on other boats that size and above with wheels (and generally liking tillers better), I've found that on 30-footers and up, I like to drive standing, not sitting, and a tiller is not conducive to that (except, as I've done, standing with it between my legs with one hand on the boom--sail furled under power).
On a big boat, the binnacle can hold all of your electronics right in front of your face, and your binocs and beer... The wheel is nice to stand behind for all-around visibility, and is less intrusive to the cockpit. Folding wheels are really neat--but the hinges must be made of 24-carat gold!
Ever seen the depth of the swim platform on walk through transom? On a thirty footer I'll bet the distance from where you might be able to locate gudgeons/mount the rudder, to where you would steer in the cockpit with a tiller is 5 feet. That's a long tiller to be dealing with in a narrow transom opening. You'd need a custom tiller and rudder designed to account for the transom issues, which translates into $$$$$$$$$.
If on the other hand, if you're dealing with an older C30 with a standard transom, then the rudder/tiller issues may not be as much a problem. You may need to modify the stern rail and purchase the custom rudder and tiller but I would think the change is pretty cut- and-dried.
As for the 250, the same open transom issues apply but not to the same extent as on a 30 footer. I would still keep the wheel on either one, although why anyone put a wheel on a 25 foot sailboat is anyone's guess.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.