I usually aim for the side to avoid water/pee splashing out.
Also, I don't think dick size and powerful/loud streams are necessarily related.
Interesting note: foreskin definitely affects the stream. I'm uncut, and when I piss without pulling back my foreskin, the pee flows through it, making the stream heavier/thicker, but slower. This stream sounds heavy when it hits the water. When I do pull back my foreskin, the stream is thinner, faster, and makes a higher pitched sound when it hits the water. I guess the same happens to other guys, right?