I prefer flemish, and not just for looks. I've had too many endless loop strings break under the end loop servings. On flemish, the string is right there in front of your eye, so you can keep a lookout for fraying. Also, a 16 strand endless loop only has 8 strands in each loop. A flemish has all 16 strands running thru the loops so, theoretically anyway, it's stronger. I've never broken a flemish string.

Endless is lighter and gives a little more speed, but that's not enough advantage to overcome it's disadvantages, IMO.