Wax Free Toilet Seals - different mfgs/styles

Would like to eliminate the wax rings on the toilets in my house. Would like to use the wax-free toilet seals. Understand there are a few different brands on the market. Has anyone compared the performance of the different brands?

Fluidmaster has the #7500, #7503, and #7504
What are the differences between each of these 3 part no's? Fluidmaster website does not provide any info at all. Assume the 7503 is 3" and #7504 is 4"? What is the #7500?

Fernco also makes a seal (#FTS-3 (3") and #FTS-4 (4")).

Do any of these have have "better quality" o-rings, seals? Is one brand "heavier duty" than another? Will one last longer? Any comments anyone can provide would be helpful.

I really don't know if any waxless rings are better than anyother, but I have used Fluidmaster rings with no problems. There are no moving parts so I can't see how anything will wear out.

For everyone's info, I found out from Fluidmaster that the #7503 is for 3" diam. pipe, #7504 is for 4" diam pipe, and the #7500 is a combination kit that fits 3 & 4" pipes (uses a 3" kit with an intermediate pipe insert & o-ring to bring it up to 4" diam).