Noise from external oil boiler?

I am thinking of installing an externally-sited oil combi boiler. Does anyone know how their noise compares with the noise from (say) an internal kitchen oil boiler (which I currently have). I don't want to put this boiler in and then find it is a noise-nuisance for either me or my neighbours when we might be in our gardens. Any body got any experience of these outside boilers? Also how well do they weather since they are outside all the time. Are there more maintenance issues in the longer-term?