I take a filter when I want to be able to drink from streams and do not use any drops. I use the filter in part so I can have ice cold water from a snow melt stream. Drops take time to work and take even longer in ice cold water. In hot weather the water may not be cold by the time it is safe when using drops. In water that isn't cold most drops or tablets take 15 minutes, for ice cold water it takes more like 30 minutes. More questionable water should be given longer. When the air is 90-110F the water won't be very cold by the time you can safely drink it.

Because of all that. I much prefer a filter rather than drops. I used to carry a Sawyer Squeeze, but now use the Sawyer Mini. It is about two ounces, so the weight penalty is quite small. I leave the syringe home since I find that I can use one of my water bottles to back flush it if it needs cleaning.

The filters like the Squeeze and the Mini reportedly can sometimes be difficult to get going again after having been stored for a long period. So always see that it flow before a trip where you may need to depend on it. Also their effectiveness may be compromised if they are allowed to freeze when still wet, so guard against freezing.

I have used my Mini and my Squeeze pretty extensively for backpacking and before that my Sweetwater filter. They all have been good in situations where I have used them. I use them a lot for backpacking. It is only on certain bike tours where I find they have enough advantage that I bother to carry them.