At 3/16” thickness, the Harmony mat is not as thick as some other yoga mats (like Jade Fusion), but it still cushions your knees a lot more than lower-quality alternatives. The Jade Harmony yoga mat is likely to be soft enough for people who don't have any pre-existing problems with their knees.
The Jade Harmony is made of open-cell rubber, which gives it the grip that's great for wet conditions such as hot yoga. The Harmony will dry out if left in direct sunlight or in the back of your car uncovered on hot days, which will ruin the grip and shorten the lifespan of your mat considerably.
The Harmony is made of natural tree rubber, so it will smell like rubber at least for the first few uses. It does air out after a while, but if you're really sensitive to smells, this mat might not be for you.
The Jade Harmony yoga mat is biodegradable, and after about a year of every-day use you will start to notice grooves in the mat in the spots where your hands and feet usually are, and bits of rubber will start to come off. If you want a yoga mat that lasts for decades, then you should consider getting a non eco-friendly version.
The Manduka eKO has a textured surface that repels sweat. This makes it good for use in dry conditions, because the sweat will sit on the surface of the mat, causing it to be more slippery than open-cell mats (open-cell surfaces absorb moisture). The closed-cell surface on the Manduka is easier to clean and reduces the risk of accumulating bacteria in its pores.
The Aurorae Classic is firm, eco-friendly, and provides a good grip in dry conditions. Aurorae has great customer service, and give a 2 year warranty on all mats.
Aurorae does provide a bag of non-slip rosin to improve the grip for use in wet conditions, but you will have to reapply it throughout your workout. When used in dry conditions, it provides good traction with both the floor and your hands and feet.
The Aurorae Classic Extra Thick is 1/4" thick, which provides great support for your knees and joints, while being firm enough to provide good support.