Practice a lot with each one from both the sitting and kneeling positions. Don't worry about what's theoretically optimal unless you are a racer. Find out what gives you comfortable paddling pleasure.
I always take a straight and a bent on day trips or wilderness trips. The bent is for the 90+% of the time I'm just doing forward strokes on flatwater. I've been using bents while kneeling for 30 years, and that's what I prefer.
I use straight paddles when in rapids, when I want turning control on twisty streams, when I want leverage in lake wind and waves, and when I want to push-pole off the bottom.
What is really sub-optimal is swinging heavy weight tens of thousands of times in a day's paddle. Therefore, I like carbon paddles. However, if you can afford only one carbon, I would spend that on a ZRE Power Surge bent shaft - the paddle you will be swinging the most on all those forward strokes.
A decent straight wood paddle with chip resistant edges, though heavier, can serve the straight paddle purposes I mentioned above just fine. Several good wooden paddle companies have been mentioned.
Reflective Hull Decals
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