Cadillac has added this comparative info to the ATS site:
The BMW 328i uses the N20 engine (2L, 4 cylinder turbo) and appears to be clearly under-rated from the factory, making around 226-240 hp at the wheels in dyno tests. That makes it a 280+ hp engine as delivered; compare to the 270hp from the ATS LTG. Some test drivers prefer the 328i to the 335i because the 328i has better balance and similar power.
Meanwhile, the upcoming ATS engine is a brand new 2L turbo version of the new 2.5L normally aspirated 4. But if the new ATS engine (LTG) is as tunable as its LHU and LNF cousins, it will quickly be tuned to 300+ hp as they are. Of course the BMW engine can be tuned as well.
Same weight, similar engine power, BMW has an 8 speed transmission, while the Cadillac ATS arrives with the 6-speed because the 8-speed isn’t ready yet.
What about the Premium ATS and the BMW 335i?
On paper, the 318 hp Cadillac ATS engine also appears to have more power than the 3L Turbo 335i’s engine which is rated at 300 hp. On paper.
Be sure that the BMW 335i’s engine output is also suspect, and likely makes 320+ hp. The 335i uses the N55 3L V6, with a dual-scroll turbo instead of the dual turbos from the N54 3L V6. In comparative tests, the 335i’s N55 V6 made 276 hp at the wheels on the dyno, or 320+ hp at the crank.