I have been commuting by a bike for 6 months on a 9 speed bike. It has a standard squared taped BB and cranks screwed on it. Now I have heard those Hollowtech 2 cranks and BB and how they can improve efficiency and putting bearings outside BB (not sure if I am saying it correctly). So how good they are? I could actually feel the improvement when I changed from a 32mm tyre to a 23 mm high pressure tyre couple of months ago. I am thinking of upgrading if worthwhile. Thanks.
They are easier to install and maintain, and depending can be lighter. However, it's not likely that you will notice any great difference in efficiency commuting on them. Probably not even 10% of the difference you would notice in a tire change (assuming the old bottom bracket and cranks were in good working order).