Cast iron gas boiler versus high efficiency gas boiler for heat

[Mark Berge]

I am getting estimates on replacing a old oil boiler with a new gas boiler to heat the rental house. House is 1000 square feet with baseboards. Have gotten estimates $11,000 to replace with a gas high efficiency boiler. I'm thinking maybe cast iron boiler would be less expensive and simpler to maintain? Any feedback. The house was built in 1964 and has 3 br, 2 bath sfam det in north jersey.