I have always been of the opinion that you should shoot at the highest resolution your equipment is capable of. Once you have those master copies, you can downsize to whatever the use of the material dictates. Even if your computer does not have the power to edit 4K, most any machine can utilize one of several free video file converter programs to do a 1080 downsample.
For example if you shoot 4K for a project (and archive the 4K masters)... but only deliver 1080 to the client, because that resolution is all the client required... all is good because the client got what he needed. But then, 2 years later the client calls and says they want to use some high resolution footage from that shoot... well then you can be the F'n hero and reply, "We actually did shoot in 4K, anticipating your being able to utilize it in the future. So, no need to re-shoot, we'll just re-edit that archived material... here's your quote to do that." ?