I see that you're still waiting for input

It's up to the builder as both systems have their pros and cons.
Here are a few observations :
• Single cable systems are adequate for speeds below 50 MPH.
• Dual (twin) cable systems are recommended for speeds above 50 MPH. The cables can be adjusted to remove most of the backlash (free play) found in single cable systems.
This reduction of backlash helps minimize rudder flutter and the resulting handling instability.
• Hydraulic systems have a small footprint, zero backlash and are rated for higher speeds.
With so many types of steering available, it's easy to get confused. Here's a link to help you select a system :
The hydraulic systems fetch a premium price. Here are a few links to a supplier we've dealt with in the past. Don't let the company's name scare you off. They delivered the goods !!
• Hydraulic :
• Mechanical :
We installed a hydraulic system since space was at a premium and speed potential was an issue. Here are a few photos of our installation :

We had many clearance issues installing a Teleflex NFB Dual Cable setup with opposing Port and Starboard cables. Exhaust hoses
were right where we wanted to install the cables and they couldn't make the tight radius bend. The solution was to upgrade to a
Teleflex SeaStar hydraulic system. To mount the cylinder within the stringers, we fabricated a slave tiller arm which connects to
the central tiller arm via an adjustable tie bar. It's not a Hot Rod unless its got some custom parts !

Visible in this photo are two 3/8" annealed copper tubes. They're retained by bulkhead fittings bolted through the stainless
steel transom support uprights. Click here for more photos.
My apologies for the lengthy post !
__________________
Paul Kane Chelsea, PQ
Building the Glen-L Hot Rod :
http://www.boats.chelseacoachworks.com