We used the Playtex Drop Ins system with both of our children. It's our plan for baby #3 (but sometimes babies have other ideas, so we'll see how it goes!).
I preferred drop ins, because as a breastfeeding mother (exclusively) for the first year, and also as a working mom (teacher), I wanted to be able to pump directly into the drop in liner. I didn't want daycare to have to thaw out a big sleeve of milk, pour it into bottles throughout the day (hind/fore milk separation...is it getting shook up enough? Did some spill -- painful when you spend so much time pumping, etc.), have some of it go to waste from having too much thawed out, etc. So for my kids, I pumped directly into the drop ins liners, froze them using the Playtext Storage Kit, as soon as the liner was frozen, I took the disks off the top to reuse them, and put the frozen sleeve of milk in to a larger ziplock bag. I would take the large ziplock bags to daycare, where they would pull out a sleeve of milk for each feeding (or two sleeves, depending on baby's needs).
It's also nice to only have the nipples to wash as opposed to a full bottle. The liners do cost money, though, so that could be an expense to consider, but most people pay money for the larger storage bags for their breastmilk anyway.
I suppose a bigger question would be how much long term milk storage will you need to do? That might make a difference with the bottle type you choose. If you pump directly into bottles, you may need quite a few to have enough bottles to pump into. We had 2 Playtex bottles at daycare and 2 at home, and that was sufficient for us, since the liners were the key.