When it comes to clears, there are several things that I look for.
1. I want it as clear as possible. If I paint something red for example, I don't want to put clear on it and have orange. I want it to look RED.
2. I want it to hold up. It will need some flexability, to avoid peeling from the metal going through the temp ranges, and also don't want it to chip easily when bumped.
3. I don't want it blowing off in the wind. It has to stick!
4. I want shrinkage to be at a minimum.
I recently did a test spray of 2 different clears for comparason of the appearance. This was 2 weeks or so ago. Of course, I left a small amount in the mixing cups when done. Last night, I went out to the garage and came across the cups with the clear in the bottoms. One of the cups had a clear that was actually "Clear", as in "little or no distortion". The other cup had clear that looked, well let's say, "milky" is a good term. Both had relatively little shrinkage, but the appearance was what got me. I also had used the clearer one last weekend, and left about 1/2" in a small cup. It was still clear as could be. It wasn't as flexable, but was still clear.
We spray clear to protect and provide a good gloss, not to change the color.