The best boiler is one which has been well installed by a competent steam pro. The pro will usually select the boiler from a local stocking distributor. He will determine the size from the combined total of radiation (EDR).
Generally boiler problems result from bad installation trying to save money for either the installer, or the customer. Unfortunately any cost savings are quickly eaten up by inefficiency, and lost sleep due to water-hammer.
You will want to discuss with the installer whether to have an atmospheric, or a power burner depending on how soundproof the boiler is.--NBC