It's not just that the drops are cheaper (and they are). I also like the fact that with the drops I have more fine control to adjust the dose to the particular volume of water I'm treating and to the amount of treatment I guesstimate that I might want. So for example, if I have water that's not particularly nasty looking and one of my water vessles is a 20-oz gatorade container, at the same time I'm mixing up treatment for one or more other containers I might put 4 or 5 drops each together for the gatorade bottle.
Not that big a deal I guess but --- combined with being cheaper in the first place it just seems like a better idea.
The one occasional annoyance with the liquid is when I run out of part A while I still have some part B left, or vice versa. In at least one case it was due to a slow leak in a bottle, and this might be what happens all of the time in such cases, I'm not sure. You do want to take a little care with the bottles that they don't get too abused along the way.
I tried repackaging into lighter bottles once, but way too much of a PITA for me, ran out of A.M. too soon on my trip and it resulted in just more logistics concerns on a long journey. Maybe fine for trips of a week or so.