There are a lot of comments in here along the lines of "log whatever you want. Nobody but you cares." I'm not sure how the OP feels (and I realize this is an old thread), but I have the same question as the OP and the reason is because, as a new diver, I am looking at near-future training and seeing requirements from the agencies for certain minimum numbers of dives. 25 dives for an SDI Advanced Scuba Diver. 40 dives before you can take Rescue Diver. 50 dives before you can get the Master Scuba Diver card. 100 dives before you can take Solo Diver.
So, what I log matters to me because, apparently, it does matter to the agencies. I understand that the agency is not going to look at my log, it's the instructor who I am trying to get training from that may or may not.
Some comments in this thread have been along the lines of "the instructor doesn't care about your log book. They care about the skills you display in the water." So, if I go to an instructor - who doesn't know me - and I have 100 dives written down in my log book and I tell them I want to take Solo, are they going to take me somewhere to get in the water and evaluate my skills before they tell me if they'll let me take the course? That seems somewhat unlikely. It seems MOST likely that they would talk to me about my experience and maybe glance at my log book. Skim it just to make sure it passes the Sniff Test, so to speak.
So I'm still uncertain about what to log. I took the Advanced Buoyancy Control class. It was in a pool and I burned a whole tank floating around at about 10' practicing buoyancy and trim exercises. Should I log that as a dive?
I rented a tank last weekend and went to the pool on my own and spent an hour or so floating around at 10' testing out some new gear and practicing my buoyancy and trim with a different rig configuration than I've used before. Should I log that as a dive?
And, to reiterate, when I ask whether I should log it, I'm really asking, should I put it in my dive log AND count it in my dive total towards, just as one example, going to the shop where I've done my training and saying "okay, I've logged 40 dives and taken the required First Aid/CPR/Oxygen course, can I enroll in the Rescue Diver class now?"