Difference between P08 and P28

[FR33K]

Im currently running an OBD1 b16a engine with a PO8 ECU.

Im doin a bit of research so I make sure i get the right ECU to suit this engine.

Now ive been offered a virgin P28 ECU and i was wondering if this is the correct one ?

As after doing a bit of research ive discovered that (and please correct me if im wrong):

P28 = single cam vtec - U.S. model.(can be chipped to work with a B16a)

P08 = single cam - jdm models (same as the p28, also can be chipped to work)

therefore, buying a P28 ECU for my b16a would be a waste of money ?? when i should just get my ECU chipped ? (i havent checked if it has been yet)

and the only other difference is that using a P08 ECU on an OBD1 b16a - it needs to be chipped to run the 4 wire O2 sensor ??

which leaves me with another question.. if my ECU isnt chipped... how could it be running the o2 sensor (unless its a single wire o2) - something ill have to figure out when the weather cools down !!

The other difference between the 2 is that po8 has no knock sensor ? and p28 does ?

I guess the bottom line is - what STANDARD ECU should I be getting to suite my engine..

sorry for the long list of questions *confused*