I think
@mas985 has the right idea. They're all black tubes on the roof. You're not going to get a significantly warmer pool from one or another brand. So it comes down to:
1. price
2. warranty
3. mounting
4. connections
1 and 2 are obvious. Here's what I mean by:
3. mounting: How does it attach to the roof? Do the mounts need to penetrate your roofing material? Does the array need tie downs for the wind load? What is the wind load capability of the array? Does this matter where you live? How does the mounting handle expansion and contraction of the array?
and
4. connections: How do the panels connect? Are the connections "UV-proof?" Solar heaters most often fail at these connections, especially the "radiator hose and clamp" type of connectors.
So those are some questions you can use for comparison.
It was for the reasons above I chose Heliocol. They have a great mounting system that didn't need to penetrate my roof felt. The mounting hardware handles all the wind load (of which I have plenty) and also allows the array to expand and contract in all directions. The connectors are really smart, using internal o-rings that are not subjected to sunlight, so are far superior to the radiator hose type. The little tubes are user repairable.
It looks like Heliocol and SunStar are under the same parent company, but I don't know how their qualities compare. I think they both have the 12 year warranty. I trust Heliocol and would recommend them highly. But sorry, I don't have direct experience with the two brands you're looking at.
I installed my panels myself. So I have a bit of experience in that area, but it doesn't sound like you're looking into DIY. Let me know otherwise.