I have reviewed the Comply S series a little over a year ago (see the review here) and compared it to the T and Tx series. At the time I have came to the conclusion that my personal preference is still the original T series in general while on some occasion, I do find the Tx series to work well to add warm to analytical IEM while S series provides easier fit. The reason for my preference for the T series is simply - it is the least intrusive when it comes to sonic effect. Like any eartips, foam tips also affect the IEM sound as the foam itself tends to absorb more treble and add warm to the overall sound, which can be a negative trait if the IEM is already warm sounding. But even with the T series, it is still impossible to avoid some level of treble absorption. The Ts series, while not really aims to 'fix' that issue, has actually turned out to be the least intrusive of all the Comply foam I have used (and I have used almost every models of them).
Ts400 (left, all middle sized) next to T200 (right, S, M, L each a pair)
According to Comply, the new spherical shape on the Ts series designed to provide "improved comfort and easy insertion". So lets start by examining whether Comply Ts is indeed more comfortable than the old T / Tx / S series. Looking at the Ts shape, one would think the slightly biggest 'waist' on the Ts might put more pressure on the ear canal and make it less comfortable than the slimmer T / Tx / S series. But the actual situation is kind of on the opposite. Because now only the waist of the Ts series is making the contact with the skin (instead of the whole surface like the older series), there is actually less feeling of pressure / fullness in the ear canal. Essentially, Ts 'disappears' easier than the old series. As for easy insertion, I think that part is pretty obvious on its own. The spherical shape with a smaller opening means you can push the foam in without the need to compress the foam with fingers first.
Though it does feel more comfortable and easier to insert, it is not really why I like about the Ts series. Comply has always been pretty comfortable on the fit, so getting better isn't that big of a deal. As long as you are not required to constantly take the IEM in and out of your ears, I would think easier to insert is also mostly just a bonus. The real surprise for me comes in the unlikely place that the new Ts series is much less intrusive (sonic wise) than any of the other Comply and even compared to the mod'ed pair of Shure olive I have on TF10. A few months back, a Head-fi'er shane55 experimented with Comply on Brainwavz B2 by trimming off the top of the foam (front of the inner tube), there by eliminating any issue of treble absorption (see this Head-fi post), and Ts does almost the same without any modification. The reason lies on the slimmer opening on the spherical shaped design, which compressed much less (as there is less foam around) than the older Comply and leaves a larger opening when the foam tip is in the ear canal, so the sound wave can pass through without too much of it being absorbed / damped. I won't say the Ts will be superior than the trimmed Comply, but the leaving the foam tip unmoded means the waxed protective surface on the foam tips will be left intact to prolong the lifespan of the foam tips. After all, Comply is not know to last forever.
S400 (left), Tx400 (top), T400 (right) and Ts400 (bottom)
Overall, I really like the new Ts series and can't recommend it enough. Sure, it is still a rather expensive option compared to the longer lasting Shure olive or simple silicone eartips. But at least now there is an option of minimum sonic compromise for those who don't mind spending more for the extra comfort and ease of fit. The Ts series, in many sense, is truly the best of Comply yet.