Why are we doing this? Well pure curiosity is in there somewhere, but the hope is that we can learn lessons from the differences between these two, quite similar, aeroplanes that can be fed into both flying training and aeroplane design towards minimising future fatal departures from controlled flight - something that we'd all like to see.
You appear to be concentrating on the aircraft. What about the pilots? As a high number of 152's are used for training they will usually have a more experienced pilot who is very current and has performed - recently - many landings etc.
150's are not often used for training nowdays. Potentially it's a low hour private owner, not doing circuits daily.