What heat source should I use for my indoor brooder in the middle of winter? I am putting the brooder in a spare bedroom.
In my opinion the brooder should be set up so that it has one spot warm enough in the coolest conditions and cool enough in the warmest conditions. In your spare bedroom that should be fairly easy to achieve. I brood outside and those temperature swings can be a challenge. If you can keep one area warm enough and another area cool enough I find the chicks are very capable of managing temperatures themselves. Overheating can be as dangerous as being too cool.
The brooder should be big enough for them to grow. I don't know how many you are getting, what breeds, or at what age you plan to put them outside. They grow really fast. It should also have a cover unless the walls are ridiculously tall. By two weeks they can typically fly several feet if they want to.
We all have our favorite heat sources to use. In my opinion which one is not as important as that it be installed properly. Anytime you use electricity there is some risk. Use proper wiring and plugs and be careful around water.
I use a heat lamp out-of-doors. If you use one I suggest you throw away that clamp and wire the lamp into place so it cannot fall. Use wire, not string that can burn or plastic that can melt. In my opinion, the major problems with heat lamps come when they are not properly secured. If you use a heating pad do not use an old one as the wiring inside can become brittle and break, causing a short. Also, make sure there is not an automatic shut-off after a couple of hours. The height of heat plates needs to be adjusted properly, also how many chicks of what age can get on it?
In my opinion they can all work if they are set up properly. I'd suggest your question should not be so much which one to use, but once you decide which one you should ask how to set it up properly. Include information like how many chicks of what breed and how long you plan to keep them in your house. Also, what is the temperature in that spare bedroom?