When our atf 55eb needed servicing I bought a ts 55ebq, (the ts75 didn't exist then). (The B in the typename stands for Brake and is only available on 220v models, but the other features are the same). The changes between those models were significant and made it much more enjoyable to use.
The ts has a springloaded riving knife, so you don't need to dissassemble it to make plunge cuts in the middle of a board.
The ts has a plug it cable, so you can more easily switch the cable and hose for using other machines with such a cable (routers/sanders)
The ts has toolles slop-adjustment for the guiderail (you don't need to adjust this often, but handy nonetheless)
The ts has a fastfix lever, that locks the spindle and keeps the blade plunged at the right depth for blade replacement. (very handy)
The ts has a green splinterguard block on the offcut side of the blade (which can only be used for non-bevel cuts, but handy if needed)
The ts has a round dustport that can swivel and which allows you to use both the 27 mm and the 36 mm vacuum hoses; the atf has an oval metal dustport where you have to squeeze the end of the 27mm hose into.
Also with the introduction of the ts saw, they also introduced the new type guiderail, allthough the atf saw also works on the newer type rail, I find that it's steel base damages the green glidestrips on the rail a bit, and when you then use a ts saw on the same rail, it makes it's magnesium base wear faster.
But the model you are comparing to the atf is a later model, the ts R which has the same features as the ts55, but a few others added:
The tsr has a wider bevel-range (the atf and ts are limited to 0°-45°)
The tsr has a different depth adjustment which reads both the on and off the rail cutting depth, and which can be zeroed accurately.
The tsr has a different splinterguard for the offcut side that doesn't protrude as much.
The tsr has a redesigned body, with a different dustport so you can saw closer to a wall.
The tsr has a differrent riving knife, which still is springloaded but is supposed to make it easier to allign a guiderail for longer cuts, when the rail isn't long enough for the entire cut.
The tsr is a new model, and there were a few issues after the introduction in the us with some saws.
Personally I wouldn't go for a atf saw at this time, and if you don't need the upgrades the R model gives, and don't care for the extra warranty a new tool gives; I would look for a good TS model.
