Siblings in Polk Audio's Reserve series, so they share a family sound. It comes down to size, output and price.
| Area | Better | Why |
|---|
| Bass | A | Polk R300 digs deeper - 65Hz against 75Hz. |
| Amplifier needs | evenly matched | Similar sensitivity (87dB vs 87dB) - both want much the same power. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Price | A | Polk R300 is cheaper - $449 against $649, about 31% less. |
A Polk R300 B Polk Audio Reserve R350
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Polk R300 has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 75Hz anyway, so judge these on the other rows instead. Think about the whole system, not just the speakers: the roughly $200 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.