New combi boiler/water heater system recommendations?

[Andy D.]

I'm replacing the aging boiler and hot water heater systems in a MA multi-family rental property in the next few months, going through the MassSave discount program. Does anyone have any feedback regarding combination boiler/water heater units? I'd love to have side-by-side wall-mounted units to free up basement floor space, but this would be my first time with combination units and I assume they're not all created equal. Feedback welcome and appreciated!