I currently have a newer model trident 15 with a rudder installed. Like mentioned, safety can be an issue when coming in, or going out through the surf. Personally, I have torn skin open like paper from mounting hardware of the rudder. That was on a big surf day and I rolled.
Needless to say, the trident 15 tracks very well. If you pick and choose your days and do light quick sessions on water, then not having a rudder is not a big deal. But if you stay on the water for long periods of time in all kinds of conditions, I would recommend a rudder. Most of my experience comes aboard peddle drive Hobies's, so paddling is not necessarily my forte. In very adverse conditions like high wind and swell working against you, I personally prefer a rudder. That is actually the only time I might even deploy the rudder. The Trident 15 is a great ride, but also like a sail compared to the Trident 13 due to it sitting higher on the water and more surface area to create drag. If you have a working meter, then I say roll with the rudder. Conversely, fish finders might not be necessary, but they sure are nice. Every once in a while turning the meter off and going old school is kinda cool though. Hope this helps you make your decision. I think every body nailed the real world advantages and disadvantages.