US has 382hp and 369 lb-ft of torque for the current O1 variant.
The M2 variant is 375hp and 384 lb-ft of torque (and 398 lb-ft with electrical assistance – boost)
Means a loss of 7hp, but a gain of 15 lb-ft (29 lb-ft with boost) of torque.
So kinda a wash, assuming no O2 high TU2 pops out of nowhere and surprises everyone with actual increases. 0-60 might see a .1-.3 second difference from the increased torque (maybe).
Personally, Id need to see the reliability of the TU2. Yeah its got port injection now in addition to direct, but that comes at a cost of increased complexity, and this dual system is new in BMW engine design. The B58 (the TU especially) is turning out to be one of the most reliable engines BMW has ever made. The TU2s new injection system could change that.
Assuming no O2 and it indeed ends up being the M2, Im just fine with my B58TUO1 with MH on my 23. Everyone is chomping at the bit for port injection, but that is really only noticeable if you plan on modding it extensively. For us regular folks, the difference is pretty minimal.