The zip lock bag method is a cheap and easy method to feed. Biggest problem I've had with it is you spill a lot when removing a bag to inspect the hive...
Regarding the hive top feeders, Miller style, I've been told by commercial beeks that the style with the entrance to the feeder in the middle is much more effective than the style with the entrance at one end. Reason being is in colder weather, bees can come straight up from the cluster to feed, instead of having to go to an end. And since heat rises, the bees who leave cluster to gain feed might not chill as they go straight up, as opposed to moving to an end to get to feed.
This year I have ten of those newer style plastic, Miller type feeders. The entrance runs down the middle, lengthwise. There is a nice piece of wire that fits into grooves in the plastic so bees cannot get out into the feed tray. the wire screws down to hold it in place. I'll know by season's end what I think of them.
Do a search for hive top feeders, there is another thread here that had a good discussion on them.
Regards,
Steven