Joe, I think a lot of people who play pool for a living prefer the measles, or formerly the red triangle, because it comes with the set of Super Aramiths. Likewise, they prefer the blue circle when playing with the Centennial balls.
Red circles, on the other hand, do not have one manufacturer. Apparently, one red circle does not have to be the same as the next.
All that being said, I usually always played with a red circle.
My sentiments exactly.... Red circles vary in size, weight, and texture because, like you said, they are made by several manufacturers. The red Triangles that used to come with Aramith Pro's (prior to the measle ball) were good cue balls and they weighed the same as Centennial Blue Circles.
We had this conversation way back on RSB and I dug this up. I weighed red circles against blue circles. Like I said, Blue Circles weigh the same as Red Triangles (and I am assuming the measles ball weighs the same as a Red Triangle....).
"Recently we weighed three red circles and three blue circles.
All 3 red's weighed 155 grams/ball
All 3 blue's weighed 170 grams/ball
As I've insisted for a long time the blue weighs more than the red."
Check out the thread at http://groups.google.com/group/rec.sport.billiard/browse_thread/thread/f833f2bd7a82bc23/b178f3f9a4803ad1?hl=en&q=red+circle+blue+cue+ball+grams+group:rec.sport.billiard
Tom Simpson, the instructor, was the creator of Elephant Balls and some aim training balls. He probably knows as much as anyone in the country about pool balls and he weighs in with a couple of good posts where he contacted two manufacturers for the straight answer.