I had my Weil McLain steam boiler replaced in 2016. The original was 37 years old and after doing some research online, and talking to a plumber friend, I went with a Weil McLain. He mentioned that Weil McLain is still one of the best residential steam boilers around, and my 37 year old boiler certainly didn't owe me anything.

The new boiler was almost a direct replacement, just one size smaller. The original was oversized for the house, which isn't the best way to run a steam system. The fact that it was pretty much a direct replacement meant that the install was much easier (no need to relocate the flue, water supply, gas supply, etc. You'll find that the person doing the installation, and whether they do it right, is equally if not more important than the brand of boiler.

Check out https://heatinghelp.com/, specifically "The Wall" on that page. It is a great source of info regarding all heating systems, but particularly steam systems.

Edited to add: Make sure you calculate the EDR (Equivalent Direct Radiation) to determine the correct size boiler for your house. The EDR (in square feet) is calculated by the size of all your radiators. You then size the boiler based on the amount of steam (in square feet) it can produce. You don't want it to be too oversized as this can actually increase fuel costs, and cause short-cycling of the boiler, which can shorten it's life. If the quotes you are getting were just a direct replacement without the companies calculating the EDR, you should look for additional quotes from companies that take this into account. Look for someone that specializes in steam systems.

Thanks very much.

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"Are you sure we're going fast enough?" - Emil Zatopek