welcome aboard mate.
re rudders, I have em on most of my SIKs and reckon they are invaluable for controling 'glide' into where i want to cast.
A lot also depends on the tracking ability of the yak you paddle, - without a rudder, many tend to want to turn into the wind all the time (weathercocking) causing the paddler to make a lot more corrective strokes to keep going where he or she wants to. This increases paddler fatigue and reduces enjoyment of paddling.
I would recommend you try the yaks in various conditions before you choose one and if you can afford it, get one with a rudder. they really are worth the added expense. (IMHO)