Simple can be good, and if the room-to-room radiation balance is near-perfection, running it as a single zone primary/secondary using an ErgoMax or TurboMax as the hydraulic separator the controls are dead-simple (a 2 pump, no valves system.) And a medium to low mass boiler behind it it'll downright kill any non-condensing non-modulating hot-water heater based system on efficiency. Iif the radiation balance ISN'T good, micro zoning with either additional pumps & 1 checkvalve per pump or a zone-valving scheme carries no efficiency penalty, where it otherwise would if un-buffered.
Polaris isn't cheating on it's steady state specs- it's just an irrelevant spec. When used strictly as a hot water heater it only scores an EF of 0.84 (84% average efficiency). Steady state thermal efficiency with continuous flow of 40-50F water entering is a useless spec for a heating system, and barely relevant to a storage-based hot water heater, since in real use it only sees the cold-flow at the heat exchanger while the water is running. During recovery as the temp rises the combustion efficiency falls. The raw combustion efficiency is highly dependent on the temperature of the water entering the heat exchanger. With natural gas exhaust the cold end of the HX has to be ~90F to hit 95% efficiency, and at 120F (the minimum you'd ever keep a hot water tank) it's already fallen to ~88%. And that's just raw combustion efficiency, no disounting for jacket losses, etc. If your staple-up needs 140F water and returns 120F water, you simply can't hit 90% with a Polaris if it's oversized for the load (which it almost certainly is). If your heating system needs 150F water and returns 130F water, there's very little benefit at all to a condensing appliance at all unless you can lower the temp when the heat load is lower, but with a hot water heater based system you'll never really want to run it colder than 125F, with a ~100-105F return, which yields (best case) ~92% in raw combustion efficiency (which is about what you'd see with a mod-con and an ErgoMax at normal hot water temps.)
But with a modulating condensing boiler and a buffer tank as the hydraulic seperator (using an indirect tank as a seperate zone) you can spend most of the season at very low temps and hit 95%, even in a staple-up. A mod-con and a slab (no buffer) + indirect can hit the high-90s.
But a key component to getting those efficiencies is to size the burner appropriately to the load, and unless this is the leakiest least-well insulated 1800 foot house in NJ a Polaris is oversized, and would only squeak mid-80s efficiencies by virtue of it's thermal mass (it's self-buffered). If there's already a functional 80%+ boiler in place, for the price of a reverse indirect and another pump it'll perform nearly as well as the Polaris (even if it's a 4-5x oversized behemoth) spending may be $100 more/year, and within $200/year of a pretty-good mod-con in a 4800HDD climate. The thermal mass of the water in ErgoMax providing the same cycle lengthening function as the mass of the water in the Polaris reducing the hit from oversizing. Oversizing still hurts some, but it is no longer an efficiency-disaster. Similarly, with slab-radiant the thermal mass of the slab itself can mitigate a world of ills, but staple-up retrofits are inherently low mass, and may need a bit extra to keep cycling losses low with on/off burners (even when "right sized"), which is why reverse-indirects are can be a good solution for hot water + heating with a single boiler. If the heat load is low enough a standard hot water heater (~78-80% raw combustion efficiency) can handle the load, but the standby losses will still limit it to mid-70s efficiency- a buffered somewhat oversized 80% AFUE boiler will meet or beat it on efficiency and provide far more hot water capacity.
But every case is different, and "design by web-forum" is just plain lousy, fraught with unforeseen hazards. But knowing the options when sitting down with a real designer (who is on the hook for the results) can help.