Most hydraulic drives will be more compact at the rudder head and offer much more installation flexibility than the linear drive because the motor and pump can be mounted separately from the ram.
It's not a simple or easy choice choice between linear drive and hydraulic.
The Raymarine linear drive is a very well engineered machine. It has a long history of reliable operation. It is quiet (Very!) and works well on the Amels it is used on.
Hydraulic units have many fewer moving parts, are much simpler mechanically, are robust, powerful, and long lasting. If you select one carefully, most of the parts will be standard hydraulic system parts available all over the world. Rams, seals, hoses, etc are common to all kinds of machines and can be sourced anywhere there is any kind of industrial economy.
But be aware: The pumps used in many of the hydraulic autopilot systems can be quiet noisy. Mounting them under the berth would definitely not be a good place if you ever wanted to sleep there underway. They can be mounted remotely with longer hoses, but that increases the cost and hassle of the install.
With a linear drive, if you are cruising in remote areas and want a back up, pretty much the only thing to do is have a complete spare ready to go. With a hydraulic unit, having a spare pump and ram seals would fix 99% of anything that would ever go wrong.
If I was installing a new AP drive on my boat from scratch... I am not sure what I would do. I have installed and worked with both systems and it's a tough choice. But it is tough because both function well, and are reliable. It might come down to which one was easier to install in that application.
If my chain drive unit was to fail, I'd might replace it with a hydraulic unit. My linear drive I'd replace in kind.